Method for receiving reference signal in wireless communication system and device therefor

ABSTRACT

A method for receiving a Reference Signal (RS) performed by a User Equipment (UE) in a wireless communication system according to an embodiment of the present invention may include receiving a first RS through a first antenna port; and receiving a second RS through a second antenna port which is Quasi Co-Located (QCL)-assumed with the first antenna port, the first and second antenna ports may be QCL-assumed for at least one QCL parameter, and the at least one QCL parameter may include a reception beam related parameter.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method for receiving a reference signal of a userequipment based on QCL assumption and an apparatus for the same.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while guaranteeing user activity. Service coverage of mobilecommunication systems, however, has extended even to data services, aswell as voice services, and currently, an explosive increase in traffichas resulted in shortage of resource and user demand for a high speedservices, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive Multiple Input MultipleOutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

An object of the present invention is to improve a reception performanceof a reference signal of a terminal through Quasi-co-Location (QCL)assumption in a wireless communication system.

The technical objects to attain in the present invention are not limitedto the above-described technical objects and other technical objectswhich are not described herein will become apparent to those skilled inthe art from the following description.

Technical Solution

A method for receiving a Reference Signal (RS) performed by a UserEquipment (UE) in a wireless communication system according to anembodiment of the present invention may include receiving a first RSthrough a first antenna port; and receiving a second RS through a secondantenna port which is Quasi Co-Located (QCL)-assumed with the firstantenna port, the first and second antenna ports may be QCL-assumed forat least one QCL parameter, and the at least one QCL parameter mayinclude a reception beam related parameter.

In addition, the reception beam related parameter may include areception beam direction parameter and/or a reception beam width relatedparameter.

In addition, the second RS may correspond to an RS of a same type as thefirst RS or an RS of different type from the first RS.

In addition, when the first RS is a first Channel state information(CSI)-RS mapped to a first CSI-RS resource, and the second RS is asecond CSI-RS mapped to a second CSI-RS resource which is different fromthe first CSI-RS resource, the first antenna port corresponding to thefirst CSI-RS resource and the second antenna port corresponding to thesecond CSI-RS resource are QCL-assumed for the reception beam relatedparameter.

In addition, when the first and second RSs are a same CSI-RS mapped toan identical CSI-RS resource, the first and second antenna portscorresponding to the identical CSI-RS resource are QCL-assumed for thereception beam related parameter.

In addition, when the first RS is CSI-RS and the second RS isSynchronization Signal (SS), the first antenna port corresponding to theCSI-RS and the second antenna port corresponding to the SS areQCL-assumed for the reception beam related parameter.

In addition, when the first RS is Demodulation RS (DMRS) and the secondRS is Phase noise compensation RS (PCRS), the first antenna portcorresponding to the DMRS and the second antenna port corresponding tothe PCRS are QCL-assumed for all QCL parameters predefined.

In addition, the PCRS may correspond to a reference signal for phasetracking.

In addition, the all QCL parameters may include the reception beamrelated parameter, Delay spread parameter, Doppler spread parameter,Doppler shift parameter, Average gain parameter and/or Average delayparameter.

In addition, a same precoding may be assumed between the first antennaport corresponding to the DMRS and the second antenna port correspondingto the PCRS.

In addition, the QCL parameter which is QCL-assumed between the firstand second antenna ports may be indicated to the UE through ahierarchical QCL signaling.

In addition, when the QCL parameter is indicated through thehierarchical QCL signaling, the method may further include: beingconfigured with a plurality of first candidate QCL configurationparameter sets through Radio Resource Control (RRC) signaling; beingconfigured with a plurality of second candidate QCL configurationparameter sets selected among the plurality of first candidate QCLconfiguration parameter sets through L2 (Layer 2)/MAC (medium accesscontrol) layer signaling; and being configured with QCL configurationparameter set which is finally selected among the plurality of secondcandidate QCL configuration parameter sets through L1 (Layer 1)/PHY(Physical) layer signaling.

In addition, a user equipment (UE) for receiving a Reference Signal (RS)in a wireless communication system according to another embodiment ofthe present invention may include a radio frequency (RF) unit configuredto transmit and receive a radio signal; and a processor configured tocontrol the RF unit, wherein the processor is further configured to:receive a first RS through a first antenna port; and receive a second RSthrough a second antenna port which is Quasi Co-Located (QCL)-assumedwith the first antenna port, the first and second antenna ports may beQCL-assumed for at least one QCL parameter, and the at least one QCLparameter may include a reception beam related parameter.

In addition, the reception beam related parameter may include areception beam direction parameter and/or a reception beam width relatedparameter.

In addition, the second RS may correspond to an RS of a same type as thefirst RS or an RS of different type from the first RS.

Technical Effects

According to an embodiment of the present invention, a parameter inrelation to a reception beam is defined as a new QCL parameter; there isan effect that a reception performance is more improved in a spatialaspect of an RS of a user equipment.

In addition, according to an embodiment of the present invention, sinceGCL assumption for different types of RSs is available, which brings thesame effect as a density of a specific RS is increased, and accordingly,there is an effect that a reception performance of the corresponding RSis improved.

In addition, according to an embodiment of the present invention, sinceQCL signaling is indicated to a user equipment in a hierarchicalsignaling scheme, there is an effect that semi-static QCL indicationconsidering an instantaneous situation is available as well as signalingoverhead may be reduced.

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 5 illustrates a self-contained subframe structure to which thepresent invention may be applied.

FIG. 6 exemplifies a sub-array partition model, which is a first TXRUvirtualization model option.

FIG. 7 exemplifies a full-connection model, which is a second TXRUvirtualization model option.

FIG. 8 illustrates reference signal patterns mapped to downlink resourceblock pairs in a wireless communication system to which the presentinvention may be applied.

FIG. 9 is a diagram illustrating a service area for each TXRU.

FIG. 10 illustrates an antenna panel model in which analog beamformingis applied for each panel to which the present invention may be applied.

FIG. 11 illustrates a scheme in which a single CSI-RS resource is mappedper panel according to an embodiment of the present invention.

FIG. 12 illustrates a scheme in which a plurality of CSI-RS resources ismapped per panel according to an embodiment of the present invention.

FIG. 13 illustrates a scheme in which CSI-RS resource shared by aplurality of panels is mapped according to an embodiment of the presentinvention.

FIG. 14 is a flowchart illustrating a method for receiving an RS of a UEaccording to an embodiment of the present invention.

FIG. 15 is a block diagram of a wireless communication device accordingto an embodiment of the present invention.

MODE FOR INVENTION

Some embodiments of the present invention are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings are intended to describesome exemplary embodiments of the present invention and are not intendedto describe a sole embodiment of the present invention. The followingdetailed description includes more details in order to provide fullunderstanding of the present invention. However, those skilled in theart will understand that the present invention may be implementedwithout such more details.

In some cases, in order to avoid that the concept of the presentinvention becomes vague, known structures and devices are omitted or maybe shown in a block diagram form based on the core functions of eachstructure and device.

In this specification, a base station (BS) (or eNB) has the meaning of aterminal node of a network over which the base station directlycommunicates with a device. In this document, a specific operation thatis described to be performed by a base station may be performed by anupper node of the base station according to circumstances. That is, itis evident that in a network including a plurality of network nodesincluding a base station, various operations performed for communicationwith a device may be performed by the base station or other networknodes other than the base station. The base station (BS) may besubstituted with another term, such as a fixed station, a Node B, an eNB(evolved-NodeB), a Base Transceiver System (BTS), an access point (AP),g-NodeB (gNB), New RAT (NR) or 5G-NodeB. Furthermore, the device may befixed or may have mobility and may be substituted with another term,such as User Equipment (UE), a Mobile Station (MS), a User Terminal(UT), a Mobile Subscriber Station (MSS), a Subscriber Station (SS), anAdvanced Mobile Station (AMS), a Wireless Terminal (WT), a Machine-TypeCommunication (MTC) device, a Machine-to-Machine (M2M) device, or aDevice-to-Device (D2D) device.

Hereinafter, downlink (DL) means communication from an eNB to UE, anduplink (UL) means communication from UE to an eNB. In DL, a transmittermay be part of an eNB, and a receiver may be part of UE. In UL, atransmitter may be part of UE, and a receiver may be part of an eNB.

Specific terms used in the following description have been provided tohelp understanding of the present invention, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present invention.

The following technologies may be used in a variety of wirelesscommunication systems, such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), and Non-OrthogonalMultiple Access (NOMA). CDMA may be implemented using a radiotechnology, such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asGlobal System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data rates for GSM Evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of Electricaland Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of a UniversalMobile Telecommunications System (UMTS). 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of an Evolved UMTS(E-UMTS) using evolved UMTS Terrestrial Radio Access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-Advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present invention and that are not described in orderto clearly expose the technical spirit of the present invention may besupported by the documents. Furthermore, all terms disclosed in thisdocument may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A is chieflydescribed, but the technical characteristics of the present inventionare not limited thereto.

General System to which the Present Invention May be Applied

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

3GPP LTE/LTE-A support a radio frame structure type 1 which may beapplicable to Frequency Division Duplex (FDD) and a radio framestructure which may be applicable to Time Division Duplex (TDD).

FIG. 1(a) illustrates the radio frame structure type 1. A radio frameconsists of 10 subframes. One subframe consists of 2 slots in a timedomain. The time taken to send one subframe is called a TransmissionTime Interval (TTI). For example, one subframe may have a length of 1ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in the time domain and includes a pluralityof Resource Blocks (RBs) in a frequency domain. In 3GPP LTE, OFDMsymbols are used to represent one symbol period because OFDMA is used indownlink. An OFDM symbol may be called one SC-FDMA symbol or symbolperiod. An RB is a resource allocation unit and includes a plurality ofcontiguous subcarriers in one slot.

FIG. 1(b) illustrates the frame structure type 2. The radio framestructure type 2 consists of 2 half frames. Each of the half framesconsists of 5 subframes, a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and an Uplink Pilot Time Slot (UpPTS). One subframeconsists of 2 slots. The DwPTS is used for initial cell search,synchronization, or channel estimation in UE. The UpPTS is used forchannel estimation in an eNB and to perform uplink transmissionsynchronization with UE. The guard period is an interval in whichinterference generated in uplink due to the multi-path delay of adownlink signal between uplink and downlink is removed.

In the frame structure type 2 of a TDD system, an uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) to all subframes. Table 1 shows theuplink-downlink configuration.

TABLE 1 Uplink- Downlink- Downlink to-Uplink configura- Switch-pointSubframe number tion periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms DS U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D DD 6 5 ms D S U U U D S U U D

Referring to Table 1, in each subframe of the radio frame, “D” isindicative of a subframe for downlink transmission, “U” is indicative ofa subframe for uplink transmission, and “S” is indicative of a specialsubframe including three types of a DwPTS, GP, and UpPTS. Anuplink-downlink configuration may be classified into 7 types. Thepositions and/or number of downlink subframes, special subframes, anduplink subframe are different in each configuration.

A point of time at which a change is performed from downlink to uplinkor a point of time at which a change is performed from uplink todownlink is called a switching point. The periodicity of the switchingpoint means a cycle in which an uplink subframe and a downlink subframeare changed is identically repeated. Both 5 ms and 10 ms are supportedin the periodicity of a switching point. If the periodicity of aswitching point has a cycle of a 5 ms downlink-uplink switching point,the special subframe S is present in each half frame. If the periodicityof a switching point has a cycle of a 5 ms downlink-uplink switchingpoint, the special subframe S is present in the first half frame only.

In all the configurations, 0 and 5 subframes and a DwPTS are used foronly downlink transmission. An UpPTS and a subframe subsequent to asubframe are always used for uplink transmission.

Such uplink-downlink configurations may be known to both an eNB and UEas system information. An eNB may notify UE of a change of theuplink-downlink allocation state of a radio frame by transmitting onlythe index of uplink-downlink configuration information to the UEwhenever the uplink-downlink configuration information is changed.Furthermore, configuration information is kind of downlink controlinformation and may be transmitted through a Physical Downlink ControlChannel (PDCCH) like other scheduling information. Configurationinformation may be transmitted to all UEs within a cell through abroadcast channel as broadcasting information.

Table 2 below shows a configuration (length of DwPTS/GP/UpPTS) of aspecial subframe.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special subframe Normal cyclic Extended cyclicNormal cyclic Extended cyclic configuration DwPTS prefix in uplinkprefix in uplink DwPTS prefix in uplink prefix in uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192·T_(s) 2560·T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384·T_(s) 5120·T_(s) 5  6592 ·T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of a radio frame is only one example. The number ofsubcarriers included in a radio frame or the number of slots included ina subframe and the number of OFDM symbols included in a slot may bechanged in various ways.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

Referring to FIG. 2, one downlink slot includes a plurality of OFDMsymbols in a time domain. It is described herein that one downlink slotincludes 7 OFDMA symbols and one resource block includes 12 subcarriersfor exemplary purposes only, and the present invention is not limitedthereto.

Each element on the resource grid is referred to as a resource element,and one resource block (RB) includes 12×7 resource elements. The numberof RBs NDL included in a downlink slot depends on a downlinktransmission bandwidth.

The structure of an uplink slot may be the same as that of a downlinkslot.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 3, a maximum of three OFDM symbols located in a frontportion of a first slot of a subframe correspond to a control region inwhich control channels are allocated, and the remaining OFDM symbolscorrespond to a data region in which a physical downlink shared channel(PDSCH) is allocated. Downlink control channels used in 3GPP LTEinclude, for example, a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), and a physicalhybrid-ARQ indicator channel (PHICH).

A PCFICH is transmitted in the first OFDM symbol of a subframe andcarries information about the number of OFDM symbols (i.e., the size ofa control region) which is used to transmit control channels within thesubframe. A PHICH is a response channel for uplink and carries anacknowledgement (ACK)/not-acknowledgement (NACK) signal for a HybridAutomatic Repeat Request (HARQ). Control information transmitted in aPDCCH is called Downlink Control Information (DCI). DCI includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for aspecific UE group.

A PDCCH may carry information about the resource allocation andtransport format of a downlink shared channel (DL-SCH) (this is alsocalled an “downlink grant”), resource allocation information about anuplink shared channel (UL-SCH) (this is also called a “uplink grant”),paging information on a PCH, system information on a DL-SCH, theresource allocation of a higher layer control message, such as a randomaccess response transmitted on a PDSCH, a set of transmission powercontrol commands for individual UE within specific UE group, and theactivation of a Voice over Internet Protocol (VoIP), etc. A plurality ofPDCCHs may be transmitted within the control region, and UE may monitora plurality of PDCCHs. A PDCCH is transmitted on a single ControlChannel Element (CCE) or an aggregation of some contiguous CCEs. A CCEis a logical allocation unit that is used to provide a PDCCH with acoding rate according to the state of a radio channel. A CCE correspondsto a plurality of resource element groups. The format of a PDCCH and thenumber of available bits of a PDCCH are determined by an associationrelationship between the number of CCEs and a coding rate provided byCCEs.

An eNB determines the format of a PDCCH based on DCI to be transmittedto UE and attaches a Cyclic Redundancy Check (CRC) to controlinformation. A unique identifier (a Radio Network Temporary Identifier(RNTI)) is masked to the CRC depending on the owner or use of a PDCCH.If the PDCCH is a PDCCH for specific UE, an identifier unique to the UE,for example, a Cell-RNTI (C-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for a paging message, a paging indication identifier, forexample, a Paging-RNTI (P-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for system information, more specifically, a SystemInformation Block (SIB), a system information identifier, for example, aSystem Information-RNTI (SI-RNTI) may be masked to the CRC. A RandomAccess-RNTI (RA-RNTI) may be masked to the CRC in order to indicate arandom access response which is a response to the transmission of arandom access preamble by UE.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 4, the uplink subframe may be divided into a controlregion and a data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) carrying uplink control information is allocatedto the control region. A physical uplink shared channel (PUSCH) carryinguser data is allocated to the data region. In order to maintain singlecarrier characteristic, one UE does not send a PUCCH and a PUSCH at thesame time.

A Resource Block (RB) pair is allocated to a PUCCH for one UE within asubframe. RBs belonging to an RB pair occupy different subcarriers ineach of 2 slots. This is called that an RB pair allocated to a PUCCH isfrequency-hopped in a slot boundary.

As more communication devices require greater communication capacity, anecessity of mobile broadband communication which is more improved thanthe existing radio access technology (RAT) has been raised. In addition,the massive MTC (Machine Type Communications) that provides variousservices anytime and anywhere by connecting a plurality of devices andobjects is also one of important issues, which is considered in a nextgeneration communication. Moreover, it has been discussed a design of acommunication system in which a service and/or a UE sensitive toreliability and latency. As such, an introduction of a next generationRAT has been discussed currently, which considers enhanced mobilebroadband communication, massive MTC, Ultra-Reliable and Low LatencyCommunication (URLLC), and the like, and such a technology is referredto as ‘new RAT (NR)’.

Self-Contained Subframe Structure

FIG. 5 illustrates a self-contained subframe structure to which thepresent invention may be applied.

In TDD system, in order to minimize data transmission delay, theself-contained subframe structure as shown in FIG. 5 has been consideredin 5 Generation new RAT. The shaded area in FIG. 5 shows a downlinkcontrol region, and the dark area shows an uplink control region. Inaddition, the area not marked in FIG. 5 may be used for a downlink (DL)data transmission or an uplink (UL) data transmission. In thecharacteristics of such a structure, a DL transmission and a ULtransmission may be sequentially progressed in a subframe, a DL data maybe transmitted and a UL ACK/NACK may be received in a subframe.Consequently, a time required for retransmitting data is reduced when adata transmission error occurs, and owing to this, the delay till thelast data forwarding may be minimized.

As an example of the self-contained subframe structure which may beconfigured/setup in a system operating based on New RAT, the followingat least four subframe types may be considered. Hereinafter, thedurations existed in each of the subframe types are numerated in timesequence.

1) DL control duration+DL data duration+guard period (GP)+UL controlduration

2) DL control duration+DL data duration

3) DL data duration+GP+UL control duration+UL control duration

4) DL data duration+GP+UL control duration

In such a self-contained subframe structure, a time gap is required fora process that an eNB and a UE switch from a transmission mode to areception mode or a process that an eNB and a UE switch from a receptionmode to a transmission mode. For this, a part of OFDM symbols on thetiming switching from DL to UL may be setup as GP, and such a subframetype may be referred to as ‘self-contained SF’.

Analog Beamforming

In Millimeter Wave (mmW) band, a wavelength becomes short and aninstallation of a plurality of antenna elements is available in the samearea. That is, the wavelength in 30 GHz band is 1 cm, and accordingly,an installation of total 100 antenna elements is available in2-dimensional arrangement shape with 0.5 lambda (wavelength) intervalsin 5 by 5 cm panel. Therefore, in mmW band, beamforming (BF) gain isincreased by using a plurality of antenna elements, and accordingly,coverage is increased or throughput becomes higher.

In this case, each antenna element has a Transceiver Unit (TXRU) suchthat it is available to adjust a transmission power and a phase, andindependent beamforming is available for each frequency resource.However, it has a problem that effectiveness is degraded in a costaspect when TXRUs are installed in all of about 100 antenna elements.Accordingly, a method has been considered to map a plurality of antennaelements in a single TXRU and to adjust a direction of beam by an analogphase shifter. Such an analog beamforming technique may make only onebeam direction throughout the entire band, and there is a disadvantagethat frequency selective beamforming is not available.

As a middle form between a Digital BF and an analog BF, B number ofhybrid BF may be considered which is smaller than Q number of antennaelement. In this case, directions of beams that may be transmittedsimultaneously are limited lower than B number; even it is changedaccording to a connection scheme between B number of TXRUs and Q numberof antenna elements.

FIGS. 6 and 7 illustrate a representative connection scheme between aTXRU and an antenna element. More particularly, FIG. 6 exemplifies asub-array partition model, which is a first TXRU virtualization modeloption and FIG. 7 exemplifies a full-connection model, which is a secondTXRU virtualization model option. In FIGS. 6 and 7, TXRU virtualizationmodel represents a relation between an output signal of a TXRU and anoutput signal of an antenna element.

As shown in FIG. 6, in the case of the virtualization model in which aTXRU is connected to a sub-array, an antenna element is connected toonly a single TXRU. Different from this, in the case of thevirtualization model in which a TXRU is connected to all antennaelements, an antenna element is connected to all TXRUs. In thesedrawings, W represents a phase vector which is multiplied by an analogphase shifter. That is, a direction of analog beamforming is determinedby W. Here, mapping between CSI-RS antenna ports and TXRUs may be 1 to 1(1:1) or 1 to many (1:N).

Reference Signal (RS)

In a wireless communication system, a signal may be distorted duringtransmission because data is transmitted through a radio channel. Inorder for a reception end to accurately receive a distorted signal, thedistortion of a received signal needs to be corrected using channelinformation. In order to detect channel information, a method ofdetecting channel information using the degree of the distortion of asignal transmission method and a signal known to both the transmissionside and the reception side when they are transmitted through a channelis mainly used. The aforementioned signal is called a pilot signal orreference signal (RS).

Furthermore recently, when most of mobile communication systems transmita packet, they use a method capable of improving transmission/receptiondata efficiency by adopting multiple transmission antennas and multiplereception antennas instead of using one transmission antenna and onereception antenna used so far. When data is transmitted and receivedusing multiple input/output antennas, a channel state between thetransmission antenna and the reception antenna should be detected inorder to accurately receive the signal. Accordingly, each transmissionantenna should have an individual reference signal.

In a mobile communication system, an RS may be basically divided intotwo types depending on its purpose. There are an RS having a purpose ofobtaining channel state information and an RS used for datademodulation. The former has a purpose of obtaining, by a UE, to obtainchannel state information in the downlink, and accordingly, acorresponding RS should be transmitted in a wideband, and a UE should becapable of receiving and measuring the RS although the UE does notreceive downlink data in a specific subframe. Furthermore, the former isalso used for radio resources management (RRM) measurement, such ashandover. The latter is an RS transmitted along with correspondingresources when an eNB transmits the downlink. A UE may perform channelestimation by receiving a corresponding RS and thus may demodulate data.The corresponding RS should be transmitted in a region in which data istransmitted.

A downlink RS includes one common RS (CRS) for the acquisition ofinformation about a channel state shared by all of UEs within a cell andmeasurement, such as handover, and a dedicated RS (DRS) used for datademodulation for only a specific UE. Information for demodulation andchannel measurement may be provided using such RSs. That is, the DRS isused only for data demodulation, and the CRS is used for the twopurposes of channel information acquisition and data demodulation.

The reception side (i.e., UE) measures a channel state based on a CRSand feedbacks an indicator related to channel quality, such as a channelquality indicator (CQI), a precoding matrix index (PMI) and/or a rankindicator (RI), back to the transmission side (i.e., an eNB). The CRS isalso called a cell-specific RS. On the other hand, a reference signalrelated to the feedback of channel state information (CSI) may bedefined as a CSI-RS.

In 3GPP LTE(-A) system, it is defined that a UE reports CSI to a BS.Here, the CSI is commonly called for the information that may representa quality of a radio channel (or also referred to as a link) establishedbetween a UE and an antenna port. For example, the CSI may correspond toa rank indicator (RI), a precoding matrix indicator (PMI), and/or achannel quality indicator (CQI), and the like. Here, RI represents rankinformation of a channel, and this may mean the number of streams that aUE receives through the same time-frequency resource. Since RI isdetermined with being dependent upon long-term fading of a channel, theRI is fed back from a UE to a BS with a period longer than CQI,generally. PMI is a value that reflects a channel space property, andrepresents a precoding index that a UE prefers based on a metric such asSINR. CQI is a value that represents signal strength, and means areception SINR that is obtainable when a BS uses the PMI, generally.

In 3GPP LTE(-A) system, a BS may setup a plurality of CSI processes to aUE, and may receive CSI report for each process. Here, the CSI processmay include CSI-RS for signal quality measurement from a BS andCSI-interference measurement (CSI-IM) resource for interferencemeasurement.

The DRS may be transmitted through resource elements if datademodulation on a PDSCH is required. A UE may receive information aboutwhether a DRS is present through a higher layer, and the DRS is validonly in the case that a corresponding PDSCH has been mapped. The DRS mayalso be called a UE-specific RS or Demodulation RS (DMRS).

FIG. 8 illustrates reference signal patterns mapped to downlink resourceblock pairs in a wireless communication system to which the presentinvention may be applied.

Referring to FIG. 8, a downlink resource block pair, a unit in which areference signal is mapped may be represented in the form of onesubframe in a time domain X 12 subcarriers in a frequency domain. Thatis, in a time axis (an x axis), one resource block pair has a length of14 OFDM symbols in the case of a normal cyclic prefix (CP) (in FIG.7(a)) and has a length of 12 OFDM symbols in the case of an extendedcyclic prefix (CP) (FIG. 7(b)). In the resource block lattice, resourceelements (REs) indicated by ‘0’, ‘1’, ‘2’, and ‘3’ mean the locations ofthe CRSs of antenna port indices ‘0’, ‘1’, ‘2’, and ‘3’, respectively,and REs indicated by D′ mean the location of a DRS.

In the case that an eNB uses a single transmission antenna, referencesignals for a single antenna port are arrayed.

In the case that an eNB uses two transmission antennas, referencesignals for two transmission antenna ports are arrayed using a timedivision multiplexing (TDM) scheme and/or a frequency divisionmultiplexing (FDM) scheme. That is, different time resources and/ordifferent frequency resources are allocated in order to distinguishbetween reference signals for two antenna ports.

Furthermore, in the case that an eNB uses four transmission antennas,reference signals for four transmission antenna ports are arrayed usingthe TDM and/or FDM schemes. Channel information measured by thereception side (i.e., UE) of a downlink signal may be used to demodulatedata transmitted using a transmission scheme, such as singletransmission antenna transmission, transmission diversity, closed-loopspatial multiplexing, open-loop spatial multiplexing or a multi-userMIMO antenna.

In the case that a multi-input multi-output antenna is supported, when aRS is transmitted by a specific antenna port, the RS is transmitted inthe locations of resource elements specified depending on a pattern ofthe RS and is not transmitted in the locations of resource elementsspecified for other antenna ports. That is, RSs between differentantennas do not overlap.

In an LTE-A system, that is, an evolved and developed form of the LTEsystem, the design is necessary to support a maximum of eighttransmission antennas in the downlink of an eNB. Accordingly, RSs forthe maximum of eight transmission antennas must be also supported. Inthe LTE system, only downlink RSs for a maximum of four antenna portshas been defined. Accordingly, in the case that an eNB has four to amaximum of eight downlink transmission antennas in the LTE-A system, RSsfor these antenna ports must be additionally defined and designed.Regarding the RSs for the maximum of eight transmission antenna ports,both of the aforementioned RS for channel measurement and theaforementioned RS for data demodulation should be designed.

One of important factors considered in designing an LTE-A system isbackward compatibility, that is, that an LTE UE should operate properlyalso in the LTE-A system, which should be supported by the system. Froman RS transmission aspect, in the time-frequency domain in which a CRSdefined in LTE is transmitted in a full band every subframe, RSs for amaximum of eight transmission antenna ports should be additionallydefined. In the LTE-A system, if an RS pattern for a maximum of eighttransmission antennas is added in a full band every subframe using thesame method as the CRS of the existing LTE, RS overhead is excessivelyincreased.

Accordingly, the RS newly designed in the LTE-A system is basicallydivided into two types, which include an RS having a channel measurementpurpose for the selection of MCS or a PMI (channel state information-RS,channel state indication-RS (CSI-RS), etc.) and an RS for thedemodulation of data transmitted through eight transmission antennas(data demodulation-RS (DM-RS)).

The CSI-RS for the channel measurement purpose is characterized in thatit is designed for a purpose focused on channel measurement unlike theexisting CRS used for purposes of measurement, such as channelmeasurement and handover, and for data demodulation. Furthermore, theCSI-RS may also be used for a purpose of measurement, such as handover.The CSI-RS does not need to be transmitted every subframe unlike the CRSbecause it is transmitted for a purpose of obtaining information about achannel state. In order to reduce overhead of a CSI-RS, the CSI-RS isintermittently transmitted on the time axis.

In the LTE-A system, a maximum of eight transmission antennas aresupported in the downlink of an eNB. In the LTE-A system, in the casethat RSs for a maximum of eight transmission antennas are transmitted ina full band in every subframe using the same method as the CRS in theexisting LTE, RS overhead is excessively increased. Accordingly, in theLTE-A system, an RS has been separated into the CSI-RS of the CSImeasurement purpose of the selection of MCS or a PMI and the DM-RS fordata demodulation, and thus the two RSs have been added. The CSI-RS mayalso be used for a purpose, such as RRM measurement, but has beendesigned for a main purpose of the acquisition of CSI. The CSI-RS doesnot need to be transmitted every subframe because it is not used fordata demodulation. Accordingly, in order to reduce overhead of theCSI-RS, the CSI-RS is intermittently transmitted on the time axis. Thatis, the CSI-RS has a period corresponding to a multiple of the integerof one subframe and may be periodically transmitted or transmitted in aspecific transmission pattern. In this case, the period or pattern inwhich the CSI-RS is transmitted may be set by an eNB.

In order to measure a CSI-RS, a UE should be aware of information aboutthe transmission subframe index of the CSI-RS for each CSI-RS antennaport of a cell to which the UE belongs, the location of a CSI-RSresource element (RE) time-frequency within a transmission subframe, anda CSI-RS sequence.

In the LTE-A system, an eNB has to transmit a CSI-RS for each of amaximum of eight antenna ports. Resources used for the CSI-RStransmission of different antenna ports must be orthogonal. When one eNBtransmits CSI-RSs for different antenna ports, it may orthogonallyallocate the resources according to the FDM/TDM scheme by mapping theCSI-RSs for the respective antenna ports to different REs.Alternatively, the CSI-RSs for different antenna ports may betransmitted according to the CDM scheme for mapping the CSI-RSs topieces of code orthogonal to each other.

When an eNB notifies a UE belonging to the eNB of information on aCSI-RS, first, the eNB should notify the UE of information about atime-frequency in which a CSI-RS for each antenna port is mapped.Specifically, the information includes subframe numbers in which theCSI-RS is transmitted or a period in which the CSI-RS is transmitted, asubframe offset in which the CSI-RS is transmitted, an OFDM symbolnumber in which the CSI-RS RE of a specific antenna is transmitted,frequency spacing, and the offset or shift value of an RE in thefrequency axis.

A CSI-RS is transmitted through one, two, four or eight antenna ports.Antenna ports used in this case are p=15, p=15, 16, p=15, . . . , 18,and p=15, . . . , 22, respectively. A CSI-RS may be defined only for asubcarrier interval Δf=15 kHz.

RS Virtualization

In mmW band, a PDSCH transmission is available only to a single analogbeam direction on a time by analog beamforming. As a result, an eNB isable to transmit data only to a small number of UEs in a specificdirection. Accordingly, on occasion demands, analog beam direction isdifferently configured for each antenna port, and a data transmissionmay be performed to a plurality of UEs in several analog beam directionssimultaneously.

Hereinafter, four sub-arrays are formed by dividing 256 antenna elementsinto four equal parts, and an exemplary structure in which a TXRU isconnected to each sub-array shown in FIG. 9 is described mainly.

FIG. 9 is a diagram illustrating a service area for each TXRU.

When each sub-array includes total 64 (8×8) antenna elements in2-dimensional array shape, a region corresponding to a horizontal anglearea of 15 degrees and a vertical angle area of 15 degrees may becovered by specific analog beamforming. That is, a region in which aneNB is needed to serve is divided into a plurality of areas, and eacharea is served at a time. In the following description, it is assumedthat CSI-RS antenna port and TXRU are mapped in 1-to-1 manner.Accordingly, an antenna port and a TXRU may have the same meaning in thefollowing description.

As shown in an example of FIG. 9a , in the case that all TXRUs (antennaport, sub-array) have the same analog beamforming direction, thethroughput of the corresponding region may be increased by forming adigital beam having higher resolution. In addition, the throughput ofthe corresponding region may be increased by increasing rank oftransmission data to the corresponding region.

As shown in FIG. 9b , in the case that each TXRU (antenna port,sub-array) has different analog beamforming direction, a simultaneousdata transmission becomes available in a corresponding subframe (SF) toUEs distributed in wider area. For example, among four antenna ports,two of them are used for a PDSCH transmission to UE1 in area 1 and theremaining two of them are used for a PDSCH transmission to UE2 in area2.

FIG. 9b shows an example that PDSCH 1 transmitted to UE1 and PDSCH 2transmitted to UE2 are Spatial Division Multiplexed (SDM). Differentfrom this, FIG. 9c shows an example that PDSCH 1 transmitted to UE1 andPDSCH 2 transmitted to UE2 may be transmitted by being FrequencyDivision Multiplexed (FDM).

Between the scheme of serving an area by using all antenna ports and thescheme of serving several areas simultaneously by dividing antennaports, in order to maximize cell throughput, a preferred scheme may bechanged depending on a RANK and an MCS served to a UE. In addition, apreferred scheme may also be changed depending on an amount of data tobe transmitted to each UE.

An eNB calculates cell throughput or scheduling metric that may beobtained when serving an area by using all antenna ports, and calculatescell throughput or scheduling metric that may be obtained when servingtwo areas by dividing antenna ports. The eNB compares the cellthroughput or the scheduling metric that may be obtained through eachscheme, and selects a final transmission scheme. Consequently, thenumber of antenna ports participated in a PDSCH transmission is changedfor each SF (SF-by-SF). In order for an eNB to calculate a transmissionMCS of a PDSCH according to the number of antenna ports and reflect itto scheduling algorithm, a CSI feedback from a UE proper to it may berequested.

Beam Reference Signal (BRS) and Beam Refinement Reference Signal (BRRS)

BRSs may be transmitted in at least one antenna port p={0, 1, . . . ,7}. BRS sequence r_(l)(m) may be defined as Equation 1 below.

$\begin{matrix}{{{r_{l}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \mspace{14mu},{{8 \cdot \left( {N_{RB}^{\max,{DL}} - 18} \right)} - 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In Equation 1, l=0, 1, . . . , 13 may represents an OFDM symbol number.In addition, c(i) represents a pseudo-random sequence generator, and maybe initialized by Equation 2 on a starting point of each OFDM symbol.

$\begin{matrix}{{C_{init} = {{2^{10} \cdot \left( {{7 \cdot \left( {n_{s} + 1} \right)} + l^{\prime} + 1} \right) \cdot \left( {{2 \cdot N_{ID}^{cell}} + 1} \right)} + {2 \cdot N_{ID}^{cell}} + 1}}\mspace{79mu} {n_{s} = \left\lfloor \frac{l}{7} \right\rfloor}\mspace{20mu} {l^{\prime} = {l\mspace{14mu} {mod}\mspace{14mu} 7}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

BRRS may be transmitted in maximum eight antenna ports p=600, . . . ,607. A transmission and a reception of BRRS may be dynamically scheduledin a downlink resource allocation in xPDCCH.

BRRS sequence r_(l,n) _(s) (m) may be defined as Equation 3 below.

$\begin{matrix}{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2{c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2{c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \mspace{14mu},{\left\lfloor {\frac{3}{8}N_{RB}^{\max,{DL}}} \right\rfloor - 1}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Equation 3, n_(s) represents a slot number in a radio frame, lrepresents an OFDM symbol number in the slot, and c(n) represents apseudo-random sequence. The pseudo-random sequence generator may beinitialized by Equation 4 on a starting point of each OFDM symbol.

c _(init)=2¹⁰(7( n _(s)+1)+l+1)(2N _(ID) ^(BRRS)+1)+2N _(ID) ^(BRRS)+1

n _(s) =n _(s) mod 20  [Equation 4]

In Equation 4, N_(ID) ^(BRRS) may be set to a UE through RRC signaling.

BRS may be transmitted in every subframe, and may be transmitted indifferent analog beam directions for each port. Such a BRS may be usedfor an eNB to determine an approximate beam direction for a UE. When anapproximate beam direction for a UE is determined based on BRS, an eNBmay transmit BRRS for each of more accurate/minute analog beamdirections within the determined analog beam direction range, and maydetermine more accurate analog beam direction.

As such, the name for the reference signal used for determining ananalog beam direction for a UE is not limited to the BRS or the BRRSdescribed above, and it is apparent that the name may be substitutedby/referred to various reference signals that are usable for performingthe same function. For example, the BRS may be substituted by/referredto primary/first CSI-RS, Primary synchronization signal/sequence (PSS),Secondary synchronization signal/sequence (SSS), SynchronizationSignal/Sequence (SS) block, NR-PSS, and/or NR-SSS, and the BRRS may besubstituted by/referred to secondary/second CSI-RS.

DL Phase noise compensation reference signal (DL PCRS)

A PCRS associated with xPDSCH may be transmitted in antenna port P=60 orP=61 as it is signaled in a DCI format. The PCRS is existed only in thecase that xPDSCH transmission is associated with a corresponding antennaport, and the PCRS in this case may be a valid reference for phase noisecompensation. The PCRS may be transmitted only in physical resourceblocks and symbols to which corresponding xPDSCH is mapped. The PCRS maybe the same in all symbols that correspond to xPDSCH allocation.

For both of the antenna ports P=60, 61, PCRS sequence r(m) may bedefined as Equation 5 below.

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \mspace{14mu},{\left\lfloor {N_{RB}^{\max,{DL}}\text{/}4} \right\rfloor - 1}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In Equation 5, c(i) represents pseudo-random sequence. The pseudo-randomsequence generator may be initialized by Equation 6 on a starting pointof each subframe.

c _(init)=(└n _(s)/2┘+1)·(2n _(ID) ^((n) ^(SCID) ⁾+1)≠2¹⁶ +n_(SCID)  [Equation 6]

In Equation 6, n_(ID) ^((i)) may be determined as below when i=0, 1.

-   -   In the case that a value for n_(ID) ^(PCRS,i) is not provided by        a higher layer, n_(ID) ^((i))=N_(ID) ^(cell)    -   Otherwise, n_(ID) ^((i))=n_(ID) ^(PCRS,i)

A value of n_SCID may be set to 0, unless it is particularly determined.In xPDSCH transmission, n_SCID may be provided by a DCI formationassociated with xPDSCH transmission.

Quasi Co-Located (QCL) Between Antenna Ports

In the present invention, when a UE receives data (e.g., PDSCH), ascheme is considered for demodulating the data using a UE-specific RSlike a specific DMRS. Since such a DMRS is transmitted together withscheduled RB(s) of the corresponding PDSCH only and during only a timeduration in which a scheduled PDSCH is transmitted, there may be arestriction in reception performance in performing channel estimationonly with the corresponding DMRS. For example, for performing channelestimation, an estimation value of major large-scale parameter (LSP) ofa radio channel is required, and DMRS density may be in short to obtainonly the DMRS existed in time/frequency domain through which thescheduled PDSCH is transmitted. Accordingly, in order to support such aUE implementation, in LTE-A, the following quasi co-locationsignaling/assumption/behavior between RS ports is defined, andaccordingly this, the methods of configuring/operating a UE aresupported.

Quasi co-located and quasi co-location (QC/QCL) may be defined asfollows.

If two antenna ports have a QC/QCL relationship (or subjected toQC/QCL), UE may assume that the large-scale property of a signaltransferred through one antenna port may be inferred from a signaltransferred through the other antenna port. In this case, thelarge-scale property includes one or more of Delay spread, Dopplerspread, Frequency shift, Average received power, and Received timing.

Furthermore, the following may be defined. Assuming that two antennaports have a QC/QCL relation (or subjected to QC/QCL), UE may assumethat the large-scale property of a channel of which one symbol istransferred through one antenna port may be inferred from a wirelesschannel of which one symbol is transferred through the other antennaport. In this case, the large-scale property includes one or more ofDelay spread, Doppler spread, Doppler shift, Average gain, and Averagedelay.

That is, if two antenna ports have a QC/QCL relation (or subjected toQC/QCL), it means that the large-scale property of a wireless channelfrom one antenna port is the same as the large-scale property of awireless channel from the other antenna port. Assuming that a pluralityof antenna ports in which an RS is transmitted is taken intoconsideration, if antenna ports on which two types of different RSs aretransmitted have a QCL relation, the large-scale property of a wirelesschannel from one antenna port may be replaced with the large-scaleproperty of a wireless channel from the other antenna port.

In this specification, the QC/QCL-related definitions are notdistinguished. That is, the QC/QCL concept may comply with one of thedefinitions. In a similar other form, the QC/QCL concept definition maybe changed in a form in which antenna ports having an established QC/QCLassumption may be assumed to be transmitted at the same location (i.e.,co-location) (e.g., UE may assume antenna ports to be antenna portstransmitted at the same transmission point). The spirit of the presentinvention includes such similar modifications. In an embodiment of thepresent invention, the QC/QCL-related definitions are interchangeablyused, for convenience of description.

In accordance with the concept of the QC/QCL, UE may not assume the samelarge-scale property between wireless channels from correspondingantenna ports with respect to non-QC/QCL antenna ports. That is, in thiscase, UE may perform independent processing on timing acquisition andtracking, frequency offset estimation and compensation, delayestimation, and Doppler estimation for each configured non-QC/QCLantenna port.

There are advantages in that UE may perform the following operationsbetween antenna ports capable of an assuming QC/QCL:

-   -   With respect to the Delay spread and Doppler spread, UE may        identically apply the results of a power-delay profile, Delay        spread and Doppler spectrum, and Doppler spread estimation for a        wireless channel from any one antenna port to a Wiener filter        which is used upon channel estimation for a wireless channel        from other antenna ports.    -   With respect to the Frequency shift and received timing, UE may        perform time and frequency synchronization on any one antenna        port and then apply the same synchronization to the demodulation        of other antenna ports.    -   With respect to the Average received power, UE may average        reference signal received power (RSRP) measurement for two or        more antenna ports.

For example, if a DMRS antenna port for downlink data channeldemodulation has been subjected to QC/QCL with the CRS antenna port of aserving cell, UE may apply the large-scale property of a wirelesschannel estimated from its own CRS antenna port upon channel estimationthrough the corresponding DMRS antenna port, in the same manner, therebyimproving reception performance of a DMRS-based downlink data channel.

The reason for this is that an estimation value regarding a large-scaleproperty may be more stably obtained from a CRS because the CRS is areference signal that is broadcasted with relatively high density everysubframe and in a full bandwidth. In contrast, a DMRS is transmitted ina UE-specific manner with respect to a specific scheduled RB, and theprecoding matrix of a precoding resource block group (PRG) unit that isused by an eNB for transmission may be changed. Thus, a valid channelreceived by UE may be changed in a PRG unit. Accordingly, although aplurality of PRGs has been scheduled in the UE, performancedeterioration may occur when the DMRS is used to estimate thelarge-scale property of a wireless channel over a wide band.Furthermore, a CSI-RS may also have a transmission cycle ofseveral˜several tens of ms, and each resource block has also low densityof 1 resource element for each antenna port in average. Accordingly, theCSI-RS may experience performance deterioration if it is used toestimate the large-scale property of a wireless channel.

That is, UE may perform the detection/reception, channel estimation, andchannel state report of a downlink reference signal through a QC/QCLassumption between antenna ports.

Meanwhile, a UE may assume that antenna ports 0-3 of a serving cell andan antenna port for PSS/SSS are in QCL relation for Doppler shift andaverage delay.

PDSCH Resource Mapping Parameters

A UE configured with transmission mode 10 for a given serving cell maybe configured with up to four parameter sets by higher layer signalingin order to decode a PDSCH according to detected PDCCH/EPDCCH that hasDCI format 2D which is intended for the UE and the given serving cell.

In order for the UE to determine PDSCH RE mapping and to determine PDSCHantenna port QCL when the UE is configured with Type B QCL type, the UEuses the parameter configured according to ‘PDSCH RE Mapping andQuasi-Co-Location indicator’ field value, which is described in belowTable 3, in the detected PDCCH/EPDCCH that has DCI format 2D.

In the case of a PDSCH that has no corresponding PDCCH/EPDCCH, the UEuses the parameter set indicated in the PDCCH/EPDCCH that has DCI format2D corresponding to SPS activation which is associated to determinePDSCH RE mapping and PDSCH antenna port QCL.

TABLE 3 Value of ‘PDSCH RE Mapping and Quasi-Co- Location Indicator’field Description ‘00’ Parameter set 1 configured by higher layers ‘01’Parameter set 2 configured by higher layers ‘10’ Parameter set 3configured by higher layers ‘11’ Parameter set 4 configured by higherlayers

The following parameters for determining PDSCH RE mapping and PDSCHantenna port QCL are configured through higher layer signaling for eachparameter set.

-   -   crs-PortsCount-r11    -   crs-FreqShift-r11    -   mbsfn-SubframeConfigList-r11    -   csi-RS-ConfigZPId-r11    -   pdsch-Start-r11    -   qcI-CSI-RS-ConfigNZPId-r11    -   zeroTxPowerCSl-RS2-r12 (when a UE is configured with higher        layer parameter CSI-Reporting-Type for a TDD serving cell)

In the case that a PDSCH is decoded according to detected PDCCH/EPDCCHhaving DCI format 1A that has CRC scrambled with C-RNTI intended for ause of a UE and a given serving cell, and a UE is configured with Type BQCL type for PDSCH transmission in antenna port 7, in order to determinePDSCH RE mapping and PDSCH antenna port QCL, a UE to which transmissionmode 10 for a given serving cell is set should use parameter set 1 inTable 3.

In order to decode a PDSCH corresponding to PDCCH/EPDCCH having DCIformat 1A that has CRC scrambled with SPS C-RNTI and PDSCH withoutcorresponding PDCCH/EPDCCH associated with SPS activation indicated byPDCCH/EPDCCH having DCI format 1A, a UE to which transmission mode 10for a given serving cell is set should use parameter set 1 in Table 3 inorder to determine PDSCH RE mapping and PDSCH antenna port QCL.

In order to decode a PDSCH according to detected PDCCH/EPDCCH having DCIformat 1A for a UE in a given serving cell, and to transmit a PDSCH inantenna ports 0-3, a UE set to transmission mode 10 for a given servingcell should determine PDSCH RE mapping using the lower indexedzero-power CSI-RS.

Antenna Port QCL for PDSCH

A UE configured with transmission modes 8-10 for a serving cell mayassume that antenna ports 7-14 for the serving cell is in QCL for agiven subframe for delay spread, Doppler spread, Doppler shift, averagegain and average delay.

A UE configured with transmission modes 1-10 for a serving cell mayassume that antenna ports 0-3, 5, 7-30 for the serving cell is in QCLfor Doppler shift, Doppler spread, average delay and delay spread.

A UE configured with transmission mode 10 for a serving cell isconfigured with one of two QCL types for the serving cell by higherlayer parameter QCL operation in order to decode a PDSCH according to atransmission scheme in relation to antenna ports 7-14.

-   -   Type A: For a UE, antenna ports 0-3, 7-30 of a serving cell is        in QCL for delay spread, Doppler spread, Doppler shift and        average delay.    -   Type B: For a UE, antenna ports 15-30 that corresponds to a        CSI-RS resource configuration identified by higher layer        parameter qcI-CSI-RS-ConfigNZPId-r11 and antenna ports 7-14        associated with a PDSCH is in QCL for Doppler shift, Doppler        spread, average delay and delay spread.

In the case of LAA Scell, a UE does not expect that it is configuredwith QCL type B.

Channel-State Information (CSI)-Reference Signal (CSI-RS) Definition

With respect to a serving cell and a UE that are configured withtransmission mode 9 and not configured with higher layer parametereMIMO-Type, the UE may be configured with a single CSI-RS resourceconfiguration.

In addition, with respect to a serving cell and a UE that are configuredwith transmission mode 9, configured with higher layer parametereMIMO-Type and of which eMIMO-Type is CLASS A, the UE may be configuredwith a single CSI-RS resource configuration.

With respect to a serving cell and a UE that are configured withtransmission mode 9, configured with higher layer parameter eMIMO-Typeand of which eMIMO-Type is CLASS B, the UE may be configured with one ormore CSI-RS resource configurations.

With respect to a serving cell and a UE that are configured withtransmission mode 10, the UE may be configured with one or more CSI-RSresource configuration(s). The following parameters that the UE assumesnon-zero transmission power for a CSI-RS is configured through higherlayer signaling for each CSI-RS resource configuration:

-   -   CSI-RS resource configuration identity when a UE is configured        with transmission mode 10    -   The number of CSI-RS ports    -   CSI RS configuration    -   CSI RS subframe configuration I_(CSI-RS)    -   UE assumption for a reference PDSCH transmission power P_(c) for        CSI feedback, when a UE is configured with transmission mode 9    -   UE assumption for a reference PDSCH transmission power P_(c) for        CSI feedback for each CSI process, when a UE is configured with        transmission mode 10.        In the case that CSI subframe sets C_(CSI,0) and C_(CSI,1) are        configured by higher layer signaling for a single CSI process,        P_(c) is configured for each of the CSI subframe sets of the        corresponding CSI process.    -   Pseudo-random sequence generator parameter no    -   CDM type parameter, when a UE is configured with higher layer        parameter eMIMO-Type and the eMIMO-Type is set to ‘CLASS A’.    -   Higher layer parameter qcI-CRS-Info-r11CRS, when a UE is        configured with transmission mode 10, UE assumption of CRS        antenna port that has the following parameters and CSI-RS        antenna ports:    -   qcI-ScramblingIdentity-r11.    -   crs-PortsCount-r11.    -   mbsfn-SubframeConfigList-r11.

P_(c) is an assumed ratio of PDSCH EPRE for CSI-RS EPRE when a UEderives CSI feedback and takes a value in a range of [−8, 15] dB with 1dB step size. Here, the PDSCH EPRE corresponds to symbol number for aratio of the PDSCH EPRE with respect to cell-specific RS EPRE.

A UE does not expect configuration of CSI-RS and PMCH in the samesubframe of a serving cell.

With respect to frame structure type 2 serving cell and 4 CRS ports, aUE does not expect to receive CSI-RS configuration index belonged to set[20-31] for a normal CP case or set [16-27] for an extended CP case.

A UE may assume that CSI-RS antenna port of CSI-RS resourceconfiguration is in QCL for delay spread, Doppler spread, Doppler shift,average gain and average delay.

A UE configured with transmission mode 10 and QCL type B may assume thatantenna ports 0 to 3 associated with qcI-CRS-Info-r11 corresponding toCSI-RS resource configuration and antenna ports 15 to 30 correspondingto CSI-RS resource configuration are in QCL for Doppler shift andDoppler spread.

A UE configured with transmission 10, configured with higher layerparameter eMIMO-Type and the eMIMO-Type is set to ‘class B’, in whichthe number of configured CSI resources is more than one for a single CSIprocess and having QCL type B does not expect to receive CSI-RS resourceconfiguration for a CSI process that has different value of higher layerparameter qcI-CRS-Info-r11.

BL/CE UE configured with CEModeA or CEModeB does not expect that it isconfigured with non-zero transmission power CSI-RS.

CSI Reporting Method

With an introduction of Full Dimension (FD)-MIMO (or may also bereferred to as Massive-MIMO, enhanced-MIMO, Large-Scale Antenna System,Very Large MIMO, Hyper-MIMO, etc.), an eNB may increase throughput of asystem by performing D-beamforming and the like using N (N>>1) antennaports (or corresponds to “element” according to specific port-to-elementvirtualization, and hereinafter, commonly referred to as “port” for theconvenience of description).

Currently, 3GPP Rel-13 defines CSI-RS operation (or CSI reportingoperation, each CSI process may be associated with a single CSI-RSresource and a single CSI-IM resource) of non-precoded scheme defined asClass A and CSI-RS operation (or CSI reporting operation, each CSIprocess may be associated with one or more CSI-RS resources and one ormore CSI-IM resources) of beamformed scheme defined as Class B.

In the case of Class A, in the FD MIMO system, an eNB may configureseveral CSI-RS resources to a UE in a single CSI process. A UE mergeseach of CSI-RS resources configured in a single CSI process into asingle large CSI-RS resource, not regarding it as an independentchannel, and feedbacks by calculating/obtaining CSI from thecorresponding resource. For example, in the case that an eNB configuresthree 4-port CSI-RS resources to a UE in a single CSI process, the UEmerges the configured three 4-port CSI-RS resources and assumes it as asingle 12-port CSI-RS resource. The UE feedbacks bycalculating/obtaining CSI using 12-port PMI from the correspondingresource.

Even in the case of Class B, in the FD MIMO system, an eNB may configureseveral CSI-RS resources to a UE in a single CSI process. For example,in a single CSI process, an eNB may configure eight 4-port CSI-RSresources to a UE. Different virtualizations are applied to therespective eight 4-port CSI-RS, and different beamformings with eachother may be applied. For example, assuming the case that verticalbeamforming is applied with zenith angle of 100 degrees to a firstCSI-RS, vertical beamforming may be applied to second to eighth CSI-RSswith zenith angle difference of 5 degrees, and as a result, verticalbeamforming may be applied to the eighth CSI-RS with zenith angle of 135degrees.

In this case, the UE assumes each of the configured CSI-RS resources asan independent channel, and selects one of the configured CSI-RSresources, and then feedbacks/reports by calculating/obtaining CSI basedon the selected resource. That is, a UE may select a CSI-RS resource ofwhich channel is robust among the configured eight 4-port CSI-RSresources, and calculate CSI based on the selected CSI-RS resource, andthen report it to the eNB. In this case, the UE may report the selectedCSI-RS resource through CSI-RS Resource Index (CRI) value. For example,in the case that the first CSI-RS resource channel is the strongest, theUE may set the CSI value to ‘0’ and report it to the eNB.

In order to represent the technical features described above, in Class BCSI process, the following variables may be defined. K may mean thenumber of CSI-RS resources existed in the CSI process, and Nk may meanthe number of CSI-RS resources of the k^(th) CSI-RS resource. Forexample, a UE is configured with eight 4-port CSI-RS resources, K is 8and Nk is 4 regardless of k value.

In current Rel-13, CRI indicates a specific CSI-RS resource only, but afuture CRI may be further materialized to indicate a specific portcombination. For example, it may be further materialized that CRIindicates a single CSI-RS resource selected among eight CSI-RS resourcesin a CSI process, and indicates that an additionally selected CSI-RSresource is constructed by a combination of ports #15 and #16. At thistime, assuming that the CRI may indicate a combination of ports #15 and#16 or ports #17 and #18 for each CSI-RS resource, the CRI may be set asone of 16 (=2{circumflex over ( )}4) values.

That is, the case of being configured with CRI=0 indicates a combinationof ports #15 and #16 of the first CSI-RS resource, the case of beingconfigured with CRI=1 indicates a combination of ports #17 and #18 ofthe first CSI-RS resource, the case of being configured with CRI=2indicates a combination of ports #15 and #16 of the second CSI-RSresource, the case of being configured with CRI=3 indicates acombination of ports #17 and #18 of the second CSI-RS resource, and insuch schemes, each of the combinations of CSI-RSs may be indicatedaccording to an ascending order of CRI values. In addition, finally, itmay be identified that the case of being configured with CRI=15indicates a combination of ports #17 and #18 of the last eighth CSI-RSresource.

In the case of Class A, a UE measures N antenna ports, and selectsN-port precoder by using it, and then reports the related CSI (PMI, CQI,RI, etc.) to an eNB. However, as N increases, the CSI-RS for a channelmeasurement of a UE needs to be also increased, and the related codebooksize is also increased, and consequently, feedback overhead is alsoincreased.

On the other hand, in the case of Class B, the number of CSI-RS ports isin relation to a maximum rank of a UE, rather than the number of antennaports of an eNB, and accordingly, there is an advantage that the CSI-RSports may be used without big increase of the number of CRI-RSs even inthe case that the number of antenna ports is increased. However, a beamselection needs to be performed in an eNB, and accordingly, there is adisadvantage that the robustness of beamforming may be degraded in theenvironment that mobility of a UE is high and a beam of an eNB isnarrow.

In order to compensate the disadvantage of the two techniques and tomaximize the advantage, it may be considered the hybrid CSI-RS basedscheme (or CSI reporting scheme) that uses a combination of Class A andClass B.

Assumptions Independent of Physical Channel

A UE should not assume that two antenna ports are in QCL unlessotherwise specified.

A UE may assume that antenna ports 0 to 3 for a serving cell is in QCLfor delay spread, Doppler spread, Doppler shift, average gain andaverage delay.

For the purpose of discovery signal-based measurement, a UE should notassume that there is another signal or physical channel except thediscovery signal.

In the case that a UE supports discoverySignalsInDeactSCell-r12, the UEis configured by discovery signal-based RRM measurement in a carrierfrequency applicable to a secondary cell in the same carrier frequency,the secondary cell is inactivated, and the UE is not configured byhigher layer in order to receive MBMS in the secondary cell, except adiscovery signal transmission, it is assumed that PSS, SSS, PBCH, CRS,PCFICH, PDSCH, PDCCH, EPDCCH, PHICH, DMRS and CSI-RS are not transmittedby the corresponding secondary cell until the subframe in which anactivation command is received for the secondary cell.

QCL Assumption and Signaling Method for New RAT

The UE performing the QCL operation, in the case that the UE configuredwith QCL Type B, may use LSPs estimated from a specific QCLed CSI-RSresource indicated a scheduling DCI in order to be assisted with channelestimation of a DMRS transmitted together with scheduled PDSCH. However,in the New RAT (NR) environment considered in the present invention,aperiodic CSI-RS transmission scheme is considered in the aspect thatthe transmission of CSI-RS itself is transmitted only when it isrequired departing from the conventional periodic scheme, andaccordingly, there is a problem that the RS density for being utilizedas CSI-RS for QCL assumption becomes in short significantly incomparison with the conventional system. Accordingly, hereinafter, it isproposed embodiments of various QCL operations considering aperiodicCSI-RS transmission scheme in such NR environment. Before theproposition, QCL parameters that may be defined in the NR environmentwill be described. However, the following QCL parameters are not limitedto the NR environment, but may be applied to various wirelesscommunication systems.

1. QCL Parameter

As QCL parameters considered (in the NR environment), one of thefollowings may be defined/configured.

-   -   Delay spread    -   Doppler spread    -   Doppler shift    -   Average gain    -   Average delay    -   Average angle (AA):    -   Angular spread (AS)

In the NR environment, when the analog beamforming is applied to a UEside, a new type of QCL property for an arrival angle needs to beconsidered, and accordingly, the parameters in relation to a receptionbeam such as the AA and the AS may be defined as new type of QCLparameters.

Between antenna ports in which QCL is guaranteed in the AA aspect, QCLassumption for a reception beam direction (and/or reception beamwidth/sweeping degree) is available. For example, a UE is available toreceive a transmission signal by setting a reception beam direction(and/or reception beam width/sweeping degree) of a transmission signalfrom other antenna port(s) in the same way as the AA estimated fromspecific antenna port(s) and in the similar way (in relation to this).When a UE operates as such, a reception performance may be guaranteedhigher than a specific level. Such an AA may also be replaced by a term“(Almost) Dominant arrival angle” and the like, for example.

Consequently, the QCL assumption in the AA aspect, when assuming thatthere is a specific dominant (arrival) angle ‘S’ of a signal measuredfrom a specific antenna port, it may be interpreted that the specificdominant (arrival) angle of a signal measured from other antenna port,which is QCL assumed (or has QCL relation) with this, is “almost” thesame as/similar to the CS′. That is, a receiver may in which QCLassumption is available may utilize/apply the AA estimated from thespecific indicated QCLed RS/SS to a reception process almost at it is,and consequently, there is an advantage that an implementation/operationof an efficient receiver is available.

The QCL assumption in the AS aspect between two antenna ports means thatthe AS of a specific port may be derived/estimated/applied from the ASestimated from other port which is QCLed with the corresponding port.

The AS may be distinguished into Azimuth AS and Zenith AS, and in thiscase, the AS may be separately defined or defined together for eachspecific dimension. And/or, the AS may be distinguished into departureAS and arrival AS, and may be defined separately or together with foreach distinguished AS.

In the AS aspect, between antenna ports in which QCL isguaranteed/assumed, the QCL assumption for a reception beamwidth/sweeping degree (and/or a reception beam direction) is available.For example, a UE may mean that a reception of a transmission signal isavailable by configuring a reception beam width/sweeping degree (and/ora reception beam direction) from other antenna port(s) identically orsimilarly (in relation to it) with the AS estimated from specificantenna port(s). When the UE operates as such, a reception performanceis guaranteed higher than a specific level.

In summarizing the contents described above in relation to the AA andthe AS, the AA may be interpreted as a parameter in relation to average(the most) valid/dominant beam/spatial direction/angle, and the AS maybe interpreted as a parameter in relation to beam/space/anglespectrum/range for degree of spreading of beam direction by a reflectordistribution (based/centered on AA).

Since such AA and AS are parameters used in the QCL assumption for areception beam/space/angle management function eventually, the AA andthe AS may be commonly referred to as, for example, reception beamparameters, reception beam related parameters, reception angleparameters, reception angle related parameters, reception spaceparameters, or spatial reception (Rx) parameters, and the like.

Hereinafter, for the convenience of description, the AA and the AS arecommonly called ‘reception beam related parameters’.

As reception beam related parameters, Angle of Arrival (AoA), DominantAoA, average AoA, Power Angular Spectrum (PAS) of AoA, average Angle ofDeparture (AoD), PAS of AoD, transmit/receive channel correlation,transmit/receive beamforming, spatial channel correlation, and the likemay also be defined, which have the same/similar property as the AAand/or the AS described above.

2. Inter/Intra-RS/SS QCL Relation

(In the NR environment,) At least one of the QCL parameters/propertiesdescribed above may be supported to be used in a UE operation by beingdefined/configured between specific RS/SS (e.g., between RS/SS ofdifferent types with each other among the RS/SS described below orbetween RS/SS of the same types).

-   -   PSS and/or SSS (this may be commonly called ‘synchronization        sequence/signal (SS) block’.)    -   BRS    -   BRRS    -   CSI-RS    -   PCRS (Phase noise Compensation Reference Signal)    -   DMRS

3. BRRS (Beam Refinement Reference Signal) QCL

In a beam refinement operation based on the BRRS, for channel estimationand the like for the BRRS itself, (when it is considered that a BRRStransmission in NR may have aperiodic property) it is required that RSdensity is supported such that the QCL assumption is available for aspecific QCL parameter/property (e.g., {Doppler spread and/or Dopplershift}) from much higher BRS, and so on.

As such, the RS/SS QCLed with the BRRS may be provided together when theRRC of the corresponding BRRS is configured, and this may mean thatsemi-static QCL configuration for BRRS is supported. Otherwise, in orderto provide more dynamic QCL configuration, QCL configuration of L2-level(and/or L1-level) may be configured/provided through medium accesscontrol (MAC) control element (CE) (and/or DCI) and so on for each BRRS.For example, all types of QCL configuration information of L2-level(and/or L1-level) may be provided to a UE (in real time) with fullflexibility, or a plurality of candidate QCL configuration parametersets is configured through RRC configuration and a UE is instructedthrough L2-level (and/or L1-level) signaling about which one isselected/applied/used among the parameter sets.

As an example of hierarchical QCL configuration instruction/signaling, ascheme is also available that an eNB configures a plurality of candidateQCL configuration parameter sets through RRC configuration to a UE, andfilters 2{circumflex over ( )}M (M>=1) parameter sets through L2-levelsignaling such as MAC CE primarily, and it may be instructed on whichparameter set is selected/applied/used among the parameter sets that arefiltered primarily through L1-level signaling through a specific DCI ofN-bit field to a UE. In other words, QCL configuration may behierarchized (e.g., through total third times) (or through a pluralityof times) and instructed/provided to a UE, and may be instructed throughRRC configuration primarily, L2-level signaling (e.g., MAC CE, etc.)secondarily, and L1-level signaling (e.g., DCI, etc.) thirdly. As such,hierarchized QCL configuration instruction scheme may be applied to theQCL configuration of other RS/SS in the same/similar manner as well asthe QCL configuration of the BRRS.

As such, the signaling scheme of RS/SS (e.g., BRS and/or PSS/SSS)information QCLed (with BRRS) provided for the purpose of channelestimation/measurement of BRRS through dynamic indication of L1 (and/orL2)-level may be very efficient in a wireless communication system inwhich “aperiodic or on-demand” BRRS transmission is considered.

More particularly, a transmitter may set at least one BRRS (resource(s))to a receiver in advance, and a transmitter (or an eNB) may instructinformation for a receiver to receive each BRRS dynamically throughL2-level (e.g., MAC CE) and/or L1-level (e.g., DCI). Here, theinformation for receiving each BRRS may include QCLed RS/SS information(with BRRS), for example, information of specific BRS port(s) and/orspecific PSS/SSS. As a result, there is an advantage that a transmitter(or an eNB) is able to perform a proper (aperiodic/on-demand) BRRStransmission very flexibly by considering an instantaneous situationsuch as loading of a UE and traffic/channel condition, and the like byusing BRRS transport resources that are preconfigured to a UE.

In order to support the operations described above efficiently, specificID may be provided to each BRRS (or BRRS resource) and/or each BRRSport(s), and/or specific ID may be provided to each BRS (or BRSresource) and/or each BRS port(s). Such a specific ID may be indicatedto a UE through QCL signaling for providing QCL configuration to the UEdescribed above.

When an eNB indicates RS/SS (e.g., specific BRS port(s)) informationQCLed for a specific BRRS to a UE (dynamically), the eNB may restrictQCL parameter/property to which QCL assumption is applied to a part ofthe numerated QCL parameters/properties.

For example, a UE may be restricted such that QCL assumption isavailable only for {Doppler spread, and/or Doppler shift}parameter/property. This is caused by the reason such as the case thatthere is a limitation in obtaining frequency synchronization only withthe BRRS safely. Particularly, the QCL assumption between BRRS and aspecific BRS may be support by an implementation scheme in the case thatBRRS and BRS are generated from the same oscillator.

And/or, a UE may be restricted that QCL assumption is (also) availablefor {Delay spread, and/or Average delay} parameter/property. Forexample, an eNB may configure/support the LSP of BRS QCLed with BRRS toa UE in the case that the LSP is guaranteed when it may be inferredbetween BRRS and BRS (transmitted from the same panel antenna, etc.),and accordingly, an efficient receiver implementation may be supported.

And/or, a UE may be restricted that QCL assumption is (also) availablefor {Average angle and/or Angular spread} parameter/property. Areception (analog) beam coefficients generation for receiving BRRS maybe applied by inferring from a beam coefficient generation which isapplied when receiving BRS, and accordingly, there is an advantage thatan efficient receiver implementation may be supported. Otherwise,considering that the AA of BRRS may be deviated with an angle differentfrom the AA of BRS with a specific level or higher, it may be set to aUE such that only “AS” is reflected (i.e., QCL assumption)(additionally).

4. CSI-RS QCL

In CSI-RS based CSI measurement and reporting operation, when a channelfor CSI-RS itself is measured, (considering that CSI-RS transmission mayhave aperiodic property in NR) it is required to support the QCLassumption for specific QCL parameter/property (e.g., Doppler spread andDoppler shift) from BRS or BRRS of which RS density is greater. Theinformation of RS/SS which is QCLed (with CSI-RS) may be provided whenRRC of the corresponding CSI-RS is configured together, and this may beinterpreted that semi-static QCL configuration for CSI-RS is supported.

Alternatively, in order to provide more dynamic QCL configuration, theQCL configuration of L2-level (and/or L1-level) through MAC (mediumaccess control) CE (control element)(and/or DCI) may beconfigured/provided for each CSI-RS (resource). For example, all typesof QCL configuration information of L2-level (and/or L1-level) may beprovided to a UE (in real time) with full flexibility, or a plurality ofcandidate QCL configuration parameter sets is configured through RRCconfiguration and a UE is instructed through L2-level (and/or L1-level)signaling about which one is selected/applied/used among the parametersets.

As an example of hierarchical QCL configuration instruction/signaling, ascheme is also available that an eNB configures a plurality of candidateQCL configuration parameter sets through RRC configuration to a UE, andfilters 2{circumflex over ( )}M (M>=1) parameter sets through L2-levelsignaling such as MAC CE primarily, and it may be instructed on whichparameter set is selected/applied/used among the parameter sets that arefiltered primarily through L1-level signaling through a specific DCI ofN-bit field to a UE. In other words, QCL configuration may behierarchical (e.g., through total third times) (or through a pluralityof times) and instructed/provided to a UE, and may be instructed throughRRC configuration primarily, L2-level signaling (e.g., MAC CE, etc.)secondarily, and L1-level signaling (e.g., DCI, etc.) thirdly. As such,hierarchical QCL configuration instruction scheme may be applied to theQCL configuration of other RS/SS in the same/similar manner as well asthe QCL configuration of the CSI-RS.

As such, the signaling scheme of RS/SS (e.g., BRS and/or PSS/SSS)information QCLed (with CSI-RS) provided for the purpose of channelestimation/measurement of BRRS through dynamic indication of L1 (and/orL2)-level may be very efficient in a wireless communication system inwhich “aperiodic or on-demand” CSI-RS transmission is considered.

More specifically, a transmitter may set at least one CSI-RS(resource(s)) to a receiver in advance. Instead of configuring all typesof configuration information (e.g., port number/(# of ports), scramblingID, time/frequency RE pattern, port subset (actually allocated port),QCLed (with CSI-RS) RS/SS information, and/or subframe period/offset)for CSI-RS measurement for each CSI-RS ID (or CSI-RS resourceconfiguration) semi-statically, only a part of information (e.g., portnumber/(# of ports), scrambling ID, and/or time/frequency RE pattern)among these may be configured (e.g., through RRC) semi-statically. Inthis case, a transmitter may indicate the remaining information elementsexcept the information element semi-statically configured throughL2-level (e.g., MAC CE) and/or L1-level (e.g., DCI). The remaininginformation elements may include QCLed (with CSI-RS) RS/SS information,for example, information of specific BRS/BRRS port(s) and/or specificPSS/SSS and the like. Here, semi-static configuration may mean that aspecific set among preconfigured candidate parameter sets is dynamicallyselected.

As a result, there in an advantage that a transmitter (or an eNB) isable to perform a proper (aperiodic/on-demand) CSI-RS transmission veryflexibly by considering an instantaneous situation such as loading of aUE and traffic/channel condition, and the like by using CSI-RS transportresources that are preconfigured to a UE.

In this embodiment, at least one CSI-RS (resource(s)) configured to a UEin semi-static manner may be interpreted as at least one “CSI-RScontainer(s) each with corresponding ID”. As such, transmission of each“CSI-RS container” on which aperiodic/“on-demand” CSI-RS is carried hasan advantage that efficiency of using CSI-RS transport resource ismaximized such that an eNB indicates optimal beamforming and QCLed RS/SSdynamically associated with the corresponding CSI-RS on everytransmission time.

The QCL assumption different from RS/SS may be configured/indicatedindependently for each CSI-RS resource to at least one CSI-RS resourceset to a receiver (or UE). For example, assuming that CSI-RS #1 and #2are set to a UE, it may be configured/indicated that CSI-RS #1 isQCL-assumed with specific BRS, and CSI-RS #2 is QCL-assumed withspecific BRRS. At this time, CSI-RS #1 may correspond to non-precodedCSI-RS, and/or CSI-RS for CSI-RS measurement initial step (e.g., CSI-RS#1 for hybrid CSI reporting based on CSI-RS #1 and #2), and in thiscase, it may be configured/indicated that CSI-RS #1 is QCLed withspecific BRS. On the contrary, CSI-RS #2 may correspond to CSI-RS #2configured for the purpose of link adaptation for improving transmissionefficiency by an eNB in a state that beamformed CSI-RS, and/or a UEaccess a specific BRS using serving-beam and progress beam refinementsufficiently through (subsequent) BRRS, and in this case, CSI-RS #2 maybe QCL configured/indicated with BRRS, not BRS.

And/or, in the case that a plurality of CSI-RS resources is configuredto a receiver (or a UE), QCL assumption may be configured/indicatedbetween a plurality of CSI-RS resources (for at least reception beamrelated parameters). For example, in the case that CSI-RS #1 and #2 areset to a UE, the UE may assume the QCL relation between antenna ports ofCSI-RS #1 and #2 (at least reception beam related parameters).

And/or, a receiver (or a UE) may be configured/indicated with QCLassumption between antenna ports in a single CSI-RS resource. Forexample, in the case that CSI-RS #1 is set to a UE, the UE may assumethe QCL relation between antenna ports corresponding to CSI-RS #1.

In order to support such various operations smoothly, QCL assumptionwith either one of BRS or BRRS may be selectively configured/indicatedto a CSI-RS. However, the present invention is not limited thereto, butaccording to an embodiment, QCL assumption for both of BRS and BRRS maybe configured/indicated to a CSI-RS, and a method of maximizing QCL RSdensity may also be supported together.

When an eNB indicates RS/SS (e.g., specific BRS port(s)) informationQCLed for a specific CSI-RS to a UE (dynamically), the eNB may restrictQCL parameter/property to which QCL assumption is applied to a part ofthe numerated QCL parameters/properties.

For example, a UE may be restricted such that QCL assumption isavailable only for {Doppler spread, and/or Doppler shift}parameter/property. This is caused by the reason such as the case thatthere is a limitation in obtaining frequency synchronization only withthe CSI-RS safely.

And/or, a UE may be restricted that QCL assumption is (also) availablefor {Average angle and/or Angular spread} parameter/property. This isbecause it is beneficial to reflect more stable beam with to CSI-RSreception process. Furthermore, when a beam width of CSI-RS is narrow,it may be set to a UE such that only “AS” is reflected (i.e., QCLassumption) (additionally).

And/or, a UE may be restricted that QCL assumption is (also) availablefor {Delay spread, and/or Average delay} parameter/property. This isbecause it is beneficial to reflect the QCL parameter such as BRStransmitted with wider band than CSI-RS transmission bandwidth to theCSI-RS reception process, considering the case that CSI-RS istransmitted with CSI-RS transmission bandwidth which is limited to apart of band.

5. DMRS QCL

When a UE is trying to receive DMRS-based PDSCH/EPDCCH, and the like,the channel estimation for DMRS is required, QCL assumption/signalingwith a specific CSI-RS, BRRS, and/or BRS may be supported for such DMRS.

For example, in the environment that it is determined that CSI-RSdensity is sufficient (by an eNB), it may be configured/indicated thatonly QCL between DMRS and specific CSI-RS resource(s) is applied.Alternatively, when it is considered that CSI-RS transmission hasaperiodic property and CSI-RS density is insufficient like NRenvironment, DMRS may be supported with QCL of other RS in which RSdensity is stably guaranteed in comparison with CSI-RS. In this case,DMRS may be QCLed with specific BRS, BRRS and/or PCRS, and direct QCLsignaling indicating such QCL configuration may be supported in a UE. Atthis time, the direct QCL signaling may be indicated to a UE even forspecific CSI-RS resource(s), PSS and/or SSS together/additionally aswell as the RS.

When the specific QCL configuration/indication between inter-RS/SS isprovided as described above, an inter-RS/SS QCL relationship may bedefined/configured in the format in which QCL application is availablebetween independent/separated/different RS and/or SS forspecific/individual QCL parameter. That is, when a UE assumes/appliesQCL, the UE may distinguish/change the applied QCL parameter accordingto RS/SS types that are QCLed with DMRS.

As an example, in the case that DMRS is QCLed with specific CSI-RSresource(s), a UE may be configured/indicated so as to assume/apply QCLlimitedly only for {Delay spread, Average delay, Average angle, Angularspread, and/or Average gain} parameter/property. In addition, in thecase that DMRS is QCLed with specific BRS, BRRS, PCRS, and/or PSS/SSS, aUE may be configured/indicated so as to assume/apply QCL limitedly onlyfor {Doppler spread, and/or Doppler shift}. This is because there is alimitation in estimating/applying {Doppler spread, and/or Doppler shift}parameter/property based on CSI-RS only.

As another example, in the case that DMRS is QCLed with specific BRS(s),BRRS(s), PCRS, and/or CSI-RS resource(s), a UE may beconfigured/indicated so as to assume/apply QCL limitedly only for {Delayspread, Average delay, Average angle, Angular spread, and/or Averagegain} parameter/property. In addition, in the case that DMRS is QCLedwith specific PSS and/or SSS, a UE may be configured/indicated so as toassume/apply QCL limitedly only for {Doppler spread, and/or Dopplershift}. This embodiment is applicable to the case that it guaranteesmore stable performance to estimate/apply {Doppler spread, and/orDoppler shift} parameter/property from PSS/SSS.

As another example, in the case that DMRS is QCLed with specific BRS(s),BRRS(s), PCRS, and/or CSI-RS resource(s), a UE may beconfigured/indicated so as to assume/apply QCL limitedly only for {Delayspread, Average delay, Average angle, Angular spread, and/or Averagegain} parameter/property. In addition, in the case that DMRS is QCLedwith specific BRS(s), BRRS(s), PCRS, and/or PSS/SSS, a UE may beconfigured/indicated so as to assume/apply QCL limitedly only for{Doppler spread, and/or Doppler shift} parameter/property. According tothis embodiment, in the case of specific BRS(s) and/or BRRS(s), QCLassumption is applicable for all (or most of) QCL parameters/properties,and simultaneously, in the case of specific CSI-RS resource(s), QCLassumption is applicable only for a part of limited QCLparameters/properties (e.g., except {Doppler spread, and/or Dopplershift}). As such, an eNB may differently configure/indicate applicablerange of QCL parameter/property for each RS/SS, and a part of multipleRSs/SSs are configured/indicated to be QCL-assumed with the same QCLparameter/property, and accordingly available number of RS samples maybe more increased. In this case, the most direct QCL application may beimplemented in the form that a priority is provided to a specific RS(e.g., CSI-RS), but QCL application from other RS (e.g., BRS, BRRS,and/or PCRS) may be considered together through weighted average, andthe like.

When assuming/signaling DMRS QCL (for the purpose of supportingnon-coherent joint transmission, etc.), different QCLconfiguration/indication may be applied to each specific DMRS port(s).For example, in the case that a UE is indicated with DMRS ports 7 to 10(through DL scheduling grant), the UE may be indicated such that the UEis available to be QCL-assumed with specific {BRS(s), BRRS(s), PCRS,and/or CSI-RS} for DMRS ports 7 and 8 among these, and available to beQCL-assumed with specific {BRS(s), BRRS(s), PCRS, and/or CSI-RS} forDMRS ports 9 and 10. This may be applied to the embodiment that DMRSports {7 and 8} and {9 and 10} may be transmitted from differentTransmission Reception Points (TRPs), or transmitted from differentantenna panels even in the same TRP, as a matter of fact. Through this,(non-coherent) joint transmission of various forms may be efficientlysupported.

The case may be assumed that specific DMRS is QCLed with specificCSI-RS, the corresponding CSI-RS is QCLed with specific BRS, and both ofthe DMRS QCL and the CSI-RS QCL are dynamically indicated by (separate)L1-level signaling (e.g., signaling by DCI). In this case, a timelineissue for the timing when the DMRS is QCL-assumed with the transmittedCSI-RS may occur. In other words, a timeline issue may occur that QCLwith the CSI-RS transmitted on a certain time is applied to DMRSreception/measurement.

In order to solve it, in the case that a signaling that specific DMRS(port(s)) is QCLed with specific CSI-RS ID # k is received in # n SF:

-   -   A UE may apply QCL assumption based on measurement samples of        CSI-RS ID # k received in a single SF timing (it may be limited        that this embodiment may be applied only to the case that        measurement restriction (MR) is set to be ON only for the        corresponding CSI-RS ID # k), of the corresponding CSI-RS ID # k        the most recently (successfully) received among the # n SF        timing or the previous SF timings, or    -   A UE may apply QCL assumption through combining/averaging with        measurement samples of CSI-RS ID # k of provided QCLed RS/SS        (e.g., BRS(s) and/or BRRS(s)) more prior timing (on which the        same information was provided by QCL signaling), as well as        measurement samples of CSI-RS ID # k received in a single SF        timing, of the corresponding CSI-RS ID # k the most recently        (successfully) received among the # n SF timing or the previous        SF timings.

6. PCRS QCL

PCRS is an RS defined for the purpose of phase drift adjustment/phasetracking, and may be transmitted with DMRS. A DMRS per each DMRS portgroup in which a plurality of DMRS ports is included may be interlinkedwith a single PCRS (e.g., has QCL/GCL relationship). PCRS may also bereferred as Phase Tracking (PT)-RS.

Alternatively, in the case that PCRS is GCLed with DMRS in GCL aspectdescribed below, DMRS may also be referred to as a Primary DMRS or aSecondary DMRS (or PT-RS), and PCRS may also be referred to as aSecondary DMRS or a Primary PCRS (or PT-RS).

It may be defined/configured that the QCL operation configured/indicatedto apply in order to receive/measure DMRS transmitted/scheduled togethermay be applied to the QCL required for receiving/measuring PCRS withoutany change/in the same manner. In the present disclosure, such arelationship is referred to as “genuine co-location (GCL)” relationship.That is, GCL means the QCL relationship in which not only a large-scaleparameter may be inferred between QCLed antenna ports, but also the moreparameters (e.g., small-scale parameter, etc.) may be inferred. As ageneralization, a UE may interpret that ‘GCLed (or having GCLrelationship) ports are treated as the same port, and available to bespecific time bundling and/or frequency bundling is available’. That is,in other words, an assumption of the same precoding is available to a UEby treating the ports in the GCL relationship as the same port,actually.

For example, PCRS may be defined/configured/indicated so as to beGCL-assumed with DMRS, and in this case, a UE may treat/regard the PCRSport and the DMRS port as the same port, and assume that the sameprocoding is applied to two antenna ports.

Such GCL concept will be described in more detail below in relation totransmission beam coordination and QCL.

And/or, a scheme is also available that the QCL required toreceive/measure PCRS is divided from the QCL of DMRStransmitted/scheduled together, and separate/independent QCL signalingis provided. At this time, separately divided QCL signaling may beprovided separately for each RS through DCI. Alternatively, in order toprevent aggravating DCI overhead problem, QCL signaling for PCRS may beseparated so as to be provided in semi-static scheme relatively than QCLsignaling for DMRS. For example, QCL signaling for PCRS may be providedL2-level signaling through MAC CE, and so on, and/or RRC signaling, andthe like. For example, DMRS may be configured/indicated such that QCLassumption is available with specific CSI-RS (and/or BRS and/or BRRS),or PCRS may be configured/indicated such that QCL assumption isavailable with specific (serving) BRS (and/or BRRS).

In the present disclosure, (QCLed/GCLed) (specific) RS/SS may beimplicitly indicated to be RS/SS for serving-cell/TP/beam, specifically.That is, a UE may be defined/configured such that the (QCLed/GCLed)(specific) RS/SS is RS/SS for RS/SS for serving-cell/TP/beam, and applythe QCL assumption therefor.

7. QCL Type

In the case of QCL type in LTE-A standard, an eNB configures RRC withQCL type B for CoMP operation such that a UE may perform dynamic pointselection (DPS) operation, and an eNB configures RRC with QCL type A fornon-CoMP operation such that a UE applies QCL among all RSs in a servingcell with each other.

In NR environment, an operation of being served for a virtualcell/sector formed in a specific beam direction as well as cell/TP(e.g., by analog beamforming). When such a virtual cell/sector iscommonly called “beam” for the convenience of description, it isrequired that inter-beam CoMP operation such as Dynamic “beam” selectionis also available. A particular example for this will be described byreference to FIG. 10 below.

FIG. 10 illustrates an antenna panel model in which analog beamformingis applied for each panel to which the present invention may be applied.

As shown in FIG. 10, through the transmission antenna configurationhaving “multi-panel antenna” structure, it may be assumed the situationthat specific analog beamforming is applied to each panel, and eachforms “virtual cell/sector/beam”. In such a situation that a signaltransmitted from a transmitter is not dominant in a particular beamdirection (e.g., from a particular panel) for a specific receiver, andsignal qualities of two or more beam directions show a difference withina specific level, the performance improvement may be expected throughthe DBS described above.

Accordingly, in the present disclosure, it is proposed that specific QCLtype B′ in which a receiver may support such an operation isdefined/configured, and accordingly, the receiver may perform beam-basedCoMP operation like DBS smoothly. In addition, QCL type A′ may besupported as a mode in which QCL assumption may be applied between RSsthat correspond to serving cell/TP/beam.

In summarizing the proposed contents, QCL type switching may bedefined/configured in the following forms.

A UE to which transmission mode x for serving cell/TP/beam is configured(or configured for New RAT operation) may be configured with one of thefollowing QCL types below for serving cell/TP/beam by higher layerparameter, in order to decode PDSCH according to a transmission schemeassociated with antenna ports (e.g., ports 7-14) in relation to DMRS.

-   -   Type A′: For a UE, the antenna ports in relation to BRS (and/or        BRRS and/or PSS/SSS) of serving cell/TP/beam is QCLed with at        least one of the QCL parameters/properties described above.    -   Type B′: For a UE, the antenna ports XX-YY corresponding to        CSI-RS (and/or BRS/BRRS) configuration distinguished by higher        layer parameter and the antenna ports (e.g., 7-14) in relation        to DMRS associated with PDSCH are QCLed with at least one of the        QCL parameters/properties described above.

The scheme may be also applied that QCL type B′ among the configurableQCL types is replaced by QCL type C′ described below, it is limitedlydefined such that semi-static switching between QCL type A′ and QCL typeC′ only is available, or all of QCL types A′ to C1′ are defined and asingle type is selectively configured by RRC signaling, and the like.

-   -   Type C′: For a UE, the antenna ports in relation to BRS/BRRS        (and/or PCRS) of a specific beam that corresponds to BRS/BRRS        configuration and the antenna ports (e.g., ports 7-14) in        relation to DMRS associated with PDSCH is QCLed with at least        one of the QCL parameters/properties described above.

However, it is apparent that such description in relation to QCL types Ato C may be modified/defined such that the QCL related proposal elementproposed in the present invention is reflected in various manners. Thatis, when QCL type is switching by setting A′ and B′ or QCL type C thatindicates direction QCL with specific BRS is supported(together/additionally) in addition to QCL type A′ and B′, in thedetailed description including the applicable QCL type/property, thetechnical element proposed in the present invention may bereflected/substituted and defined/modified/defined.

In the present disclosure, various RSs are referred to as BRS, BRRS,PCRS, and the like, for the convenience of description, but theapplication of the present invention is not limited thereto, but it isapparent that the present invention may also be applied to RS of otherterm having the same/similar form/function/purpose of the correspondingRS.

In addition, the control information configured/indicated in aUE/receiver may be forwarded by RRC, MAC CE, and/or DCI, and a form ofsignaling among signaling of such L1 and/or L2 level in which thecorresponding configuration/indication is provided may bedefined/configured differently/independently for each individual controlinformation.

Transmission Beam Coordination for NR and QCL

In the NR environment, single/multi point transmission may be supportedfor both of DL MIMO and UL MIMO. In addition, in the NR environment, ameasurement assumption for QCL assumption and antenna ports may beperformed. Based on this, hereinafter, intra/inter-TRP coordinationtransmission in which QCL is assumed between specific RSs will bedescribed below.

1. Intra-TRP Coordination Transmission

Various antenna panel arrangement structures have been considered in theNR environment/system. A first panel model may be distinguished as auniform 1D/2D rectangular panel array. Since a proper CSI-RSresource/port should be configured with a UE through such antenna array,an efficient closed-loop MIMO transmission may be applied based on theCSI measurement and feedback of a UE. CSI-RS port and antenna arraymapping are dependent upon eNB implementation and various mappingschemes may be existed, for example, the following schemes may beexited: (1) a CSI-RS resource per panel, (2) a plurality of CSI-RSresources per panel, and (3) CSI-RS resource mapped to a plurality ofpanel, is mapped.

FIG. 11 illustrates a scheme in which a single CSI-RS resource is mappedper panel according to an embodiment of the present invention.

The embodiment shown in FIG. 11 shows the simplest method of CSI-RSmapping that a CSI-RS resource is transmitted in a panel and CSI-RSports in CSI-RS resource may be QCL-guaranteed/assumed. That is,according to this embodiment, between (a part or all) CSI-RS ports in asingle CSI-RS resource, the QCL may be assumed/guaranteed for at least apart (e.g., parameter in relation to average gain, delay spread, Dopplerspread, Doppler shift, average delay and/or reception beam) among theQCL parameters/properties described above. Such QCLassumption/guaranteeing may be performed in the case that the sameoscillator (having related component) in order to generate a signal inCSI-RS ports (included in a single CSI-RS resource or mapped to a singlepanel).

This may be interpreted as a single (virtual) cell operation accordingto the conventional art, and the single virtual cell may be associatedwith a UE by measuring an RS port that corresponds to Radio resourcemanagement (for the convenience of description, hereinafter, referred toas ‘RRM-RS’). According to the RRM-RS and detailed RS design forpotentially aperiodic/sub band CSI-RS, in order to support a UEimplementation, a proper QCL assumption is required between CSI-RSresource and specific RRM-RS.

FIG. 12 illustrates a scheme in which a plurality of CSI-RS resources ismapped per panel according to an embodiment of the present invention.

The embodiment shown in FIG. 12 may be interpreted as multiplebeamformed CSI-RS based operation similar to Full Dimension (FD)-MIMOclass B having multiple Beamformed (BF) CSI-RS resources. Since such aplurality of CSI-RSs transmitted from a single panel is oriented todifferent beam directions, it cannot say that each CSI-RS and thecorresponding RRM-RS are in QCL always for all QCLproperties/parameters. Similar to the definition in LTE specification,in the QCL assumption between CSI-RS and RRM-RS for this case, forexample, only a part of properties/parameters such as Doppler shift andDoppler spread may be used, and this may be explicitly indicated. Sincesuch a difference is caused by different CSI-RS mapping scheme forantenna array, NR specification should support various implementationschemes of CSI-RS antenna port mapping of different purposes properly.

FIG. 13 illustrates a scheme in which CSI-RS resource shared by aplurality of panels is mapped according to an embodiment of the presentinvention.

The embodiment shown in FIG. 13 may be interpreted as the shared CSI-RSresource which is mapped to a plurality of panels so as to have morebeamforming gain in the CSI-RS transmitted by cooperative transmissionfrom a plurality of panel antennas. Such a scheme in which CSI-RS portis mapped to a plurality of panels may be particularly useful for thecase of intended to support SU-MIMO transmission for a specific UE inwhich traffic load is small. When it is assumed that a network obtainssufficient information of beamforming direction for a target UE, theCSI-RS may be used as a UE-specific beamformed CSI-RS dedicated to theUE. In order to properly support a use scenario, when QCL assumption isrequired, it is required to examine the QCL assumption between CSI-RSand RRM-RS and the way of definition or support of signaling for NRoperation.

In summarizing the contents described above, according to a CSI-RSresource mapping method for multi-panel Transmission Point (TP), variousintra-TRP coordination transmission scheme may be considered in NR. Inaddition, a proper QCL assumption between RS(s) for RRM and CSI-RS(s)set to a UE may be required to support the intra-TRP coordinationtransmission.

2. QCL Type and Signaling

In the case that QCL assumption between different antenna ports isrequired in NR in order to improve channel estimation performance, inthe embodiments shown in FIGS. 11 to 13, different QCL types and similarsemi-static configurations may be supported such as being defined in LTEspecification (UE of TM 10 is configured with QCL type A or B by RRCsignaling).

However, in the NR context, together with the CSI-RS transmission(vigorously discussed in Rel-14 eFD-MIMO) of aperiodic type which hasbeen considered, in order to use efficiently in a reception operation inUE side, it is preferable to research the QCL type which is configurablemore dynamically and the corresponding QCL assumption. In other words,each UE may be configured with specific CSI-RS resource(s) that has afew essential RRC parameters, but actual CSI-RS transmission may becontrolled by an eNB through L1-signaling. Here, the controllablecomponent may include actual transmission instance, time/frequency REpattern, number of ports, applied port numbering and/or scrambling seed.Such a dynamic CSI-RS allocation and transmission may require support ofmore flexible QCL signaling with other RS that includes RRM-RS in moredynamic scheme. That is, dynamic CSI-RS allocation and transmission forNR may require more flexible QCL signaling support for other RS thatincludes RRM-RS.

3. Other QCL Parameter/Property

In current LTE specification, five LSPs for QCL between antenna ports,that is, delay spread, Doppler spread, Doppler shift, average gain, andaverage delay are defined. Except such existing QCL parameters,especially when analog beamforming is applied in UE side, it may berequired to consider a property of a new type of arrival angle/beam forNR research.

During beam scanning/tracking procedure, a UE may select several TX-RXanalog beam pair by measuring and comparing a quality of specific DL RS(for the convenience of description, referred to as ‘RRM-RS’). An eNB(or may be referred to as gNB) may select one of UE-preferredtransmission (TX) beams in order to transmit beamformed CSI-RS or DMRSports. In this case, the UE should know which reception (RX) beamreceives these antenna ports among candidate RX beams such that the TXbeam ID corresponding to RRM-RS port is to be signaled to the UE. Inthis situation, it can be said that the RRM-RS port and the CSI-RS/DMRSport are QCLed in the aspect of dominant arrival angle according to theQCL definition as below.

-   -   In the case that the LSP of a channel through which a symbol of        an antenna port is transferred is able to be implied/inferred        from the channel through which a symbol of other antenna port is        transmitted, it can be said that two antenna ports are QCLed.

The Dominant arrival angle may determine an RX beam formationcoefficient. In addition, since an analog beam may not be dynamicallychanged on comparison with a digital beam, the Dominant arrival anglemay be regarded as LSP relatively. Without QCL assumption, a UE shouldsearch a plurality of RX beam candidates, and this is time andfrequency-consuming.

Accordingly, in the NR environment, a new type of QCL property needs tobe considered for arrival angle when analog beamforming is applied in UEside, the reception beam related parameter described above may bedefined as a new type of QCL parameter.

4. Transmission coordination between inter-RS QCL and TRP

In designing RRM-RS, in order to assist RRM-RS measurement, it should beconsidered whether a part (e.g., Doppler shift and average delay) of QCLparameters/properties obtained from synchronization signals isQCL-assumed for RRM-RS. When a UE tracks such RRM-RS(s) once, this maybe used for QCL linkage of the second level of RRM-RS for minuter beamrefinement which may be UE-specifically beamformed for the UE. Asdescribed above, it is required to be indicated that CSI-RS follows QCLlinkage for primary or secondary RRM-RS(s). When sub band CSI-RS is setto a UE, for example, it may be beneficial to follow QCL for otherCSI-RS which is transmitted in broadband.

In the current LTE specification, a UE to which TM10 having QCL type Bis configured may be scheduled to receive a PDSCH transmitted from anon-serving cell/TP as CoMP Dynamic point selection (DPS) operation. Atthis time, the DMRS for a PDSCH may be instructed to follow at least oneof CSI-RSs configured by PQI filed in a DCI and QCL. In other words, theDMRS for a PDSCH may be configured to have QCL relation with at leastone of CSI-RSs indicated by PQI field. In such a DPS operation, in thefact that an actual dynamic TRP selection is performed according to aconfigured CSI-RS resource (e.g., each CSI-RS resource configured foreach TRP) or a dynamic beam selection (DBS) is performed in a singleTRP, a similar operation to the DPS operation may be considered inNR-MIMO. This may be interpreted as intra-TRP CoMP in beam coordinationaspect.

In order to properly support these kinds of various transmissionstrategies in NR, the DMRS for PDSCH should also be explicitly indicatedto follow QCL to other RS, e.g., CSI-RS or RRM-RS, unless DMRS designfor NR study is done without requiring any other QCL supports and byguaranteeing sufficient RS density within the scheduled band.

Particularly, in order to support phase compensation at UE side owing tophase noise effect, the second level of DMRS (i.e., secondary DMRS) maybe transmitted to a scheduled PDSCH which is wanted to be distributedthroughout a time domain like several symbols of the same subcarrier.Since such secondary DMRS is an RS transmitted to support the phasecompensation at UE side, the secondary DMRS may be the conceptcorresponding to the PCRS (or PT-RS) described above. Accordingly, thesecondary DMRS may be referred to as the PCRS (or PT-RS) or substitutedby the PCRS (or PT-RS).

It may be assumed that the secondary DMRS may be QCLed with the primaryDMRS for all QCL parameters/properties, and the QCL in this case may beinterpreted to the GCL described above. Here, the GCL is available fortime/frequency bundling between antenna ports as described above, andindicates that these are the same port efficiently. As a result, a UEmay receive DMRS by assuming the same precoding between GCLed antennaports.

In summary, the first and second DMRSs are distributed/transmitted overa plurality of symbol regions (i.e., multiple time regions, e.g.,continuous time regions) in the same subcarrier region, where a GCLrelationship may be indicated/configured between the first and secondDMRSs. When the UE is indicated/configured with the GCL relationship ofthe first and second DMRSs, the UE can receive the DMRS assuming thesame precoding between the first and second DMRS ports.

The GCL relationship in the embodiment described above is interpretedwith DMRS (or data demodulation) aspect mainly, and may also beinterpreted/described PCRS (or phase compensation) mainly. That is, inthe embodiment described above, although the secondary DMRS (orPCRS/PT-RS) is used for the purpose/effect of receiving DMRS stably byincreasing DMRS density, on the contrary, the primary DMRS may be usedfor the purpose/effect of receiving DMRS stably by increasing PCRS (orPT-RS) density.

In describing the embodiment in the above-described aspect again, theprimary and secondary PCRSs (or PT-RSs) (corresponding to the primaryand secondary DMRSs) may be transmitted throughout/being distributed ina plurality of symbol domains (i.e., several time domains, e.g.,consecutive time domains) in the same subcarrier domain (i.e., the samefrequency domain), and in this case, the GCL relationship may beindicated/configured between the primary and secondary PCRSs (orPT-RSs). When a UE is configured with the GCL relationship between theprimary and secondary PCRSs (or PT-RSs), the UE may receive PCRS (orPT-RS) by assuming the same precoding in the between the primary andsecondary PCRSs (or PT-RSs) ports.

In generalizing the embodiment described above, consequently, the DMRSand the PCRS (or PT-RS) having the GCL relationship may be distributedin a time domain and transmitted to a UE in the same frequency domain,and the UE may receive the DMRS and the PCRS (or PT-RS) by assuming theGCL relationship between the DMRS and the PCRS (or PT-RS) and byassuming the same precoding. At this time, the DMRS and the PCRS (orPT-RS) which are GCLed may be named according to GCL purpose (e.g., datademodulation purpose or phase compensation purpose). In the case thatthe DMRS and the PCRS (or PT-RS) which are GCLed may be referred to asthe primary and secondary DMRSs in the case that these are in the datademodulation purpose, and may be referred to as the primary andsecondary PCRSs (or PT-RSs) in the phase compensation purpose. However,the DMRS and the PCRS (or PT-RS) which are GCLed are not limitedthereto, but may also be substituted by the RS (or RS name) having thesame purpose/function/effect.

In conclusion, to properly support various intra/inter-TRP coordinatedtransmissions, DMRS QCL to CSI-RS or RRM-RS may need to be dynamicallyindicated, unless DMRS design for NR is done without requiring any QCLsupports and by guaranteeing sufficient RS density.

It means that the GCL concept described above is available toconfigure/indicate specific “{frequency, time, space, and/orcode}-domain bundling/aggregation”,

-   -   In the case of frequency-domain bundling, a transmitter (e.g.,        eNB) may indicate bundling to a receiver (e.g., UE) with a        subcarrier level, an RB level, an RB group (e.g., RBG) level,        and/or a sub band level, and the like.    -   In the case of time-domain bundling, a transmitter (e.g., eNB)        may indicate bundling to a receiver (e.g., UE) with a symbol        level, a slot level, a (mini-) subframe level, or a subframe        group (e.g. TTI bundling) level, and the like.    -   In the case of space-domain bundling, a transmitter (e.g., eNB)        may indicate bundling to a receiver (e.g., UE) with a port/beam        level, and the like, and the ports/beams in this case may        correspond to corresponding specific RSs and/or channels (e.g.,        in the case that the same precoder should be used for nominal        ports/beams distinguished in a transmitter.).    -   In the case of code-domain bundling, a transmitter (e.g., eNB)        may indicate bundling to a receiver (e.g., UE) with specific        other sequences (e.g., generated by different scrambling        parameters) or between other cover codes (e.g., OCC).

As such, a receiver is configured/indicated with the fact that specific(available to apply {frequency, time, space, and/or code}-domainbundling) GCL assumption is available between RSs, SSs, and/or channels,the receiver may apply the GCL assumption between RSs, SSs, and/orchannels, and may improve a reception performance by {frequency, time,space, and/or code}-domain bundling. Such an operation makes it possibleto configure/indicate such GCL assumption (temporarily) in a specificcase for a receiver by an intension of a transmitter, although commonoperation is different between RSs, SSs, and/or channels, and has anadvantage that various transmission flexibilities are provided and areception performance is improved.

For example, as exemplified above, the intended operations may bedifferent between the PCRS and the DMRS (different antenna port numbermay be provided) basically (e.g., the PCRS is in the phase compensationpurpose, and the DMRS is in the data demodulation purpose), and in thecase that configuration/indication that the GCL assumption is availableis provided, the GCLed PCRS may be utilized in DMRS reception process(with the DMRS) for the data demodulation purpose, and accordingly, areception performance may be improved.

As another example, in addition to such an operation between specificRSs, according to the GCL relationship configured/indicated byconsidering the relationship of “PSS/SSS/ESS(Extended SynchronizationSignal) and/or BRS”, PSS may be utilized as a channel estimationreference signal of SSS, and accordingly, SSS reception performance maybe improved. Similarly, in the case that BRS is also configured suchthat the GCL assumption is available with specific PSS/SSS/ESS, it isavailable to improve a reception performance of the BRS through this.

In addition, the GCL assumption may be configured/indicated such that aUE may perform bundling by GCL assumption application with respect tospecific different {frequency, time, space, and/or code}-domain bundlingeven for the same RS, SS or channel.

For example, in the case that the GCL assumption is configured/indicatedfor specific time instances with respect to specific CSI-RS (resourceand/or port(s)), even in the case that actual each CSI-RS transmissionis (1-shot) dynamically indicated by a DCI, a UE may average/combine themeasurement samples between such 1-shot CSI-RS measurement throughoutthe GCLed (or GCL assumption is configured/indicated) time instances. Inthe aspect of a transmitter, with respect to the GCLed time instances,for example, this may mean that beamforming coefficients applied whenapplying each CSI-RS transmission should not be changed. Consequently,the precoder applied when transmitting each beamformed CSI-RS may betransmitted in receiver-transparent manner, but a transmitter mayguarantee that the CSI-RS in which same precoder is maintained/appliedis transmitted in the GCLed time instances. With this, there is aneffect that a receiver measures and combines the GCLed (aperiodic)CSI-RSs and secures adequate measurement samples, and through this,specific LSPs may be estimated. With the LSP estimated as such, the QCLconfiguration/indication described above is available with another RS(e.g., DMRS), and through this, the data demodulation performance basedon DMRS may be improved.

As described above, GCL indicator (e.g., GCL indication field defined inDCI) that configures/indicates GCL may be configured with 1-bit field,and the like, and may be implemented with a “toggling” form. That is,for example, in the case that a GCL indicator transmitted whileaperiodic CSI-RS transmission is triggered is ‘0’ and a GCL indicator ofCSI-RS transmission (of the same ID as the corresponding CSI-RS)transmitted/measured the most recently is also ‘0’ (i.e., a GCLindicator is not toggled), a UE may apply the GCL assumption betweenthese two CSI-RS transmission, and may performbundling/combining/averaging operation. In such a way, in the case thatthe UE also transmits a GCL indicator for a subsequent CSI-RS in a formof not toggled, the UE may perform bundling for the subsequent CSI-RScontinually. In the case that a GCL indicator for the subsequent CSI-RSis transmitted with being toggled, the UE may not perform bundling forthe corresponding CSI-RS any more.

As such, the operation that a UE determines whether to perform/applybundling according to a GCL indicator value (e.g., whether to toggle)indicated for the most recently transmitted CSI-RS may be limited to thescheme that it is determined whether to apply the GCL assumption bycomparing (by toggling) with the most recent instance in the set inwhich only the CSI-RS instances indicated by the same QCL as the QCLwith other RS (e.g., BRS and/or BRRS) of the corresponding CSI-RS (evenin the case of the same CSI-RS ID). This is because a CSI-RStransmission QCLed with other RS (e.g., BRS and/or BRRS) may be flexiblytransmitted aperiodically as described above, even in the case of thetransmission by the same CSI-RS ID. Consequently, as such, a UE may belimited to the scheme that the QCL assumption is applied within theCSI-RS transmission instances that follow the same ‘CSI-RS to other RS(e.g., BRS and/or BRRS) QCL’.

Such a limited operation may be signaling-indicated to a UE in variousmanner such as bundling is applied by collecting the CSI-RS transmissioninstances of which CSI process ID indicated by the corresponding DCIfield are the same in the case that DCI field is configured in thefollowing forms, in addition to the method that bundling is applied bycolleting the CSI-RS transmission instances of which ‘CSI-RS to other RS(e.g., BRS and/or BRRS) QCL’ are the same. In addition, as representedin the following Table, the way of determining the limited set may beimplemented with various embodiments by the DCI field which is applied.

TABLE 4 5.3.3.1.3 Format B1 DCI format B1 is used in scheduling ofxPDSCH The information below is transmitted through DCI format B1 insubframe n ... - CSI/BSI/BRI request - 3bits If an indicated value is‘000’, CSI/BSI/BRI is not requested. ▪ If an indicated value is ‘001’,this DCI format triggers BSI reporting. ▪ If an indicated value is‘010’, this DCI format allocates BRRS, and triggers corresponding BRIreport. ▪ If an indicated value is ‘011’, this DCI format allocatesBRRS, but does not trigger BRI report. ▪ If an indicated value is ‘100’,this DCI format allocates CSI-RS, and triggers corresponding BRI report.▪ ‘101’, ‘110’ and ‘111’ are reserved. ... If this format allocateseither one of CSI-RS or BRRS transmission, - process indicator - 2bits00 : {Process #0}, 01 : {Process #1}, 10 : {Process #2}, 11 : {Process#3} ...

Only a part of examples are described in the present disclosure, but theGCL relation operation may be applied by substituting QCL by GCL (andthe related definition/attribute) even for all QCL related proposedoperations described in the present invention (since the GCL concept isapplying more fortified properties than the QCL).

FIG. 14 is a flowchart illustrating a method for receiving an RS of a UEaccording to an embodiment of the present invention. In relation to thisflowchart, the description of the embodiments described above may beidentically/similarly applied, and the repeated description will beomitted.

First, a UE may receive a first RS through a first antenna port (step,S1410). Next, the UE may receive a second RS through a second antennaport which is QCL-assumed with the first antenna port (step, S1420). Atthis time, the first and second antenna ports may be QCL-assumed for atleast one QCL parameter, but the at least one QCL parameter may includea reception beam related parameter.

The reception beam related parameter may include a reception beamdirection parameter (e.g., AA) and/or a reception beam width relatedparameter (e.g., AS).

The second RS may correspond to an RS of the same type as the first RSor different type from the first RS.

As an example, the first RS may be a first CSI-RS mapped to a firstCSI-RS resource, and the second RS may be a second CSI-RS mapped to asecond CSI-RS resource. In this case, the first antenna portcorresponding to the first CSI-RS resource and the second antenna portcorresponding to the second CSI-RS resource are QCL-assumed for (atleast) reception beam related parameter.

As another example, the first and second RSs may correspond to the sameCSI-RS mapped to the same CSI-RS resource. In this case, the first andsecond antenna ports that correspond to the same CSI-RS resource areQCL-assumed for (at least) reception beam related parameter.

As another example, the first RS may correspond to CSI-RS, and thesecond RS may correspond to SS (e.g., PSS, SSS and/or ESS). In thiscase, the first antenna port corresponding to CSI-RS and the secondantenna port corresponding to SS are QCL-assumed for (at least)reception beam related parameter.

As another example, the first RS may correspond to DMRS, and the secondRS may correspond to PCRS. In this case, the first antenna portcorresponding to DMRS and the second antenna port corresponding to PCRSare QCL-assumed for ‘all’ QCL parameters predefined. Here, ‘QCLassumption is available for all QCL parameters’ may be interpreted thatthe same precoding assumption may be available between the first andsecond antennas, consequently. In other words, a UE may assume the sameprecoding between the first antenna port corresponding to DMRS and thesecond antenna port corresponding to PCRS. In this example, PCRScorresponds to a reference signal for phase tracking, and may bereferred to as PT-RS. The ‘all’ QCL parameters QCL-assumed between thefirst and second antennas may include a reception beam relatedparameter, Delay spread parameter, Doppler spread parameter, Dopplershift parameter, Average gain parameter and/or Average delay parameter.

The QCL parameter which is QCL-assumed between the first and secondantenna ports may be indicated to a UE through a hierarchical QCLsignaling. Here, the hierarchical QCL signaling means a signaling schemethat through a plurality of times of signaling, a final QCL parameter isset to a UE. For example, a UE may be configured with a plurality offirst candidate QCL configuration parameter sets through RRC signaling,first. Next, the UE may be configured with a plurality of secondcandidate QCL configuration parameter sets selected among a plurality offirst candidate QCL configuration parameter sets through L2 (Layer2)/MAC (medium access control) layer signaling. Next, the UE may beconfigured with QCL configuration parameter set which is finallyselected among a plurality of second candidate QCL configurationparameter sets through L1 (Layer 1)/PHY (Physical) layer signaling.

General Device to which Present Invention May be Applied

FIG. 15 is a block diagram of a wireless communication device accordingto an embodiment of the present invention.

Referring to FIG. 15, a wireless communication system includes a basestation (BS) (or eNB) 1510 and a plurality of terminals (or UEs) 1520located within coverage of the BS 1510.

The eNB 1510 includes a processor 1511, a memory 1512, and a radiofrequency (RF) unit 1513. The processor 1511 implements functions,processes and/or methods proposed in FIGS. 1 through 14. Layers of radiointerface protocols may be implemented by the processor 1511. The memory1512 may be connected to the processor 1511 to store various types ofinformation for driving the processor 1511. The RF unit 1513 may beconnected to the processor 1511 to transmit and/or receive a wirelesssignal.

The UE 1520 includes a processor 1521, a memory 1522, and a radiofrequency (RF) unit 1523. The processor 1521 implements functions,processes and/or methods proposed in above-described embodiments. Layersof radio interface protocols may be implemented by the processor 1521.The memory 1522 may be connected to the processor 1521 to store varioustypes of information for driving the processor 1521. The RF unit 1523may be connected to the processor 1521 to transmit and/or receive awireless signal.

The memory 1512 or 1522 may be present within or outside of theprocessor 1511 or 1521 and may be connected to the processor 1511 or1521 through various well known units. Also, the eNB 1510 and/or the UE1520 may have a single antenna or multiple antennas.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

An embodiment of the present invention may be implemented by variousmeans, for example, hardware, firmware, software or a combination ofthem. In the case of implementations by hardware, an embodiment of thepresent invention may be implemented using one or moreApplication-Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers and/ormicroprocessors.

In the case of implementations by firmware or software, an embodiment ofthe present invention may be implemented in the form of a module,procedure, or function for performing the aforementioned functions oroperations. Software code may be stored in the memory and driven by theprocessor. The memory may be placed inside or outside the processor, andmay exchange data with the processor through a variety of known means.

It is evident to those skilled in the art that the present invention maybe materialized in other specific forms without departing from theessential characteristics of the present invention. Accordingly, thedetailed description should not be construed as being limitative fromall aspects, but should be construed as being illustrative. The scope ofthe present invention should be determined by reasonable analysis of theattached claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention applied to a 3GPP LTE/LTE-A/NR system is primarilydescribed as an example, but may be applied to various wirelesscommunication systems in addition to the 3GPP LTE/LTE-A/NR system.

1. A method for receiving a Reference Signal (RS) performed by a UserEquipment (UE) in a wireless communication system, comprising: receivinga first RS through a first antenna port; and receiving a second RSthrough a second antenna port which is Quasi Co-Located (QCL)-assumedwith the first antenna port, wherein the first and second antenna portsare QCL-assumed for at least one QCL parameter, and wherein the at leastone QCL parameter includes a reception beam related parameter.
 2. Themethod for receiving an RS of claim 1, wherein the reception beamrelated parameter includes a reception beam direction parameter and/or areception beam width related parameter.
 3. The method for receiving anRS of claim 1, wherein the second RS corresponds to an RS of a same typeas the first RS or an RS of different type from the first RS.
 4. Themethod for receiving an RS of claim 3, when the first RS is a firstChannel state information (CSI)-RS mapped to a first CSI-RS resource,and the second RS is a second CSI-RS mapped to a second CSI-RS resourcewhich is different from the first CSI-RS resource, wherein the firstantenna port corresponding to the first CSI-RS resource and the secondantenna port corresponding to the second CSI-RS resource are QCL-assumedfor the reception beam related parameter.
 5. The method for receiving anRS of claim 3, when the first and second RSs are a same CSI-RS mapped toan identical CSI-RS resource, wherein the first and second antenna portscorresponding to the identical CSI-RS resource are QCL-assumed for thereception beam related parameter.
 6. The method for receiving an RS ofclaim 3, when the first RS is CSI-RS and the second RS isSynchronization Signal (SS), wherein the first antenna portcorresponding to the CSI-RS and the second antenna port corresponding tothe SS are QCL-assumed for the reception beam related parameter.
 7. Themethod for receiving an RS of claim 3, when the first RS is DemodulationRS (DMRS) and the second RS is Phase noise compensation RS (PCRS),wherein the first antenna port corresponding to the DMRS and the secondantenna port corresponding to the PCRS are QCL-assumed for all QCLparameters predefined.
 8. The method for receiving an RS of claim 7,wherein the PCRS corresponds to a reference signal for phase tracking.9. The method for receiving an RS of claim 7, wherein the all QCLparameters includes the reception beam related parameter, Delay spreadparameter, Doppler spread parameter, Doppler shift parameter, Averagegain parameter and/or Average delay parameter.
 10. The method forreceiving an RS of claim 7, wherein a same precoding is assumed betweenthe first antenna port corresponding to the DMRS and the second antennaport corresponding to the PCRS.
 11. The method for receiving an RS ofclaim 1 or 4, wherein the QCL parameter which is QCL-assumed between thefirst and second antenna ports is indicated to the UE through ahierarchical QCL signaling.
 12. The method for receiving an RS of claim11, when the QCL parameter is indicated through the hierarchical QCLsignaling, further comprising: being configured with a plurality offirst candidate QCL configuration parameter sets through Radio ResourceControl (RRC) signaling; being configured with a plurality of secondcandidate QCL configuration parameter sets selected among the pluralityof first candidate QCL configuration parameter sets through L2 (Layer2)/MAC (medium access control) layer signaling; and being configuredwith QCL configuration parameter set which is finally selected among theplurality of second candidate QCL configuration parameter sets throughL1 (Layer 1)/PHY (Physical) layer signaling.
 13. A User Equipment (UE)for receiving a Reference Signal (RS) in a wireless communicationsystem, comprising: a radio frequency (RF) unit configured to transmitand receive a radio signal; and a processor configured to control the RFunit, wherein the processor is further configured to: receive a first RSthrough a first antenna port; and receive a second RS through a secondantenna port which is Quasi Co-Located (QCL)-assumed with the firstantenna port, wherein the first and second antenna ports are QCL-assumedfor at least one QCL parameter, and wherein the at least one QCLparameter includes a reception beam related parameter.
 14. The UE ofclaim 13, wherein the reception beam related parameter includes areception beam direction parameter and/or a reception beam width relatedparameter.
 15. The UE of claim 13, wherein the second RS corresponds toan RS of a same type as the first RS or an RS of different type from thefirst RS.